Background: I own a mid-2010 Macbook Pro with an i7 processor and 8GB RAM with a 500GB 7200rpm HDD running Mac OS X Lion and decided that my next indulgence purchase would be an SSD after reading some articles and watching some videos of computers equipped with one in action. The next step was research. I knew SSDs handled erasing files differently than HDDs and each have their own controller which handles "garbage collection" along with the TRIM command. If you want to find out more about each of these things just search Wikipedia for each (e.g., garbage collection, TRIM, SSD). It does a good job of explaining how the "blocks" of an SSD work differently than the platters on a regular HDD.
Decision & Tech Notes: Anyway, I had narrowed it down between the SanDisk Extreme SSDs and the Crucial M4 based on price and performance. I looked at storagereview.com to compare the drive performance. I was leaning Crucial since I have purchased their RAM modules for each of my Macs and it has never failed me. I decided to go with the Crucial M4 based on my past experience with their RAM but also because it does not use a SandForce controller. SandForce controllers compress data to achieve high speeds, but the data must be compressible for this to work. I encrypt my drive using FileVault 2 and so it is all non-compressible. I had also read that SandForce controlellers ran into problems when TRIM was enabled with them on Macs so I steered clear since I planned on enabling TRIM for non-Apple drives for my new SSD (instructions on how to do so can be found with a simple google search). Of note, this drive is 6Gb/s or SATA III but is backwards compatible with SATA II. My mid-2010 i7 Macbook Pro only has an SATA II or 3Gb/s interface. Looking at the System Information App (called System Profiler pre-Lion) I noticed this right away, but also noticed that the "Negotiated Link Speed" was only 1.5Gb/s or SATA I speed. I figured this was because the HDD couldn't take advantage of the higher speeds anyway even though it was a 7200rpm drive. I hoped when I put the new SATA III M4 in, it would saturate the SATA II port and increase the "Negotiated Link Speed" to 3Gb/s which it did.
Install: I used Carbon Copy Cloner (love that app; again you can find instructions by googling) to copy the contents of my HDD to the new SSD. I created a bootable clone. Luckily, I had an old external drive USB to SATA connector laying around and used that to plug in the SSD to the Macbook Pro in order to clone it. What I like about Carbon Copy Clonder is that it also allows you to clone the Lion Recovery Partition which is hidden on the Mac's HDD. This is necessary if you want to use FileVault 2 and is also handy to repair the disk if need be later on. This took a few hours. I booted from the SSD just to make sure it worked correctly and sure enough it did.
Physical installation is a piece of cake. I can't say this is the first time I've cracked open my computers as I like to repair them myself if I can. I have replaced airport cards and hard drives in Macbook Pros before. I use the guides from iFixit.com. You'll need some small phillips head screwdrivers and it also calls for a Torx T6 screwdriver which I've never purchased even though it seems a lot of the screws under the hood in the Macbook Pros are this type. In this case, you can just use pliers to grab the Torx screws from the side and twist since they stick out, both to loosen them and tighten them back on. Took all of 5 minutes, if that. I took some time to clean up the dust around the fans while I was in there as well.
The last step was updating the firmware to the latest version which is 000F. I believe it came with 0309 or something like that. This was easy as well. Burned a CD containing the firmware update via the instructions on Crucial's website, typed "yes" and hit enter and viola.
Performance: Overall, I'm pleased with the drive's performance. It is certainly faster to boot up and restart and I've noticed no problems since enabling TRIM (Keep in mind that enabling TRIM for non-Apple SSDs is not sanctioned by Apple). It was not as dramatic a change as I had previously expected after reading all the rave reviews but I had kept my Macbook Pro pretty lean and so it was never really bogged down to being with. Still, it is fast, especially when accessing several things from the drive at once. Which makes sense since a HDD essentially acts like a record player and having to seek out more than one thing at once would require the "needle" to jump back and forth. I disabled safe sleep because I didn't want the contents of the RAM written to the SSD every time it went to sleep since SSDs have limited write cycles. That would have been 8GB written every time it went to sleep. A benefit of this is that the computer sleeps almost immediately. The downside, of course, is that if the battery should die while it is asleep and not plugged in, I will have lost that session but I never let the battery die anyway; and even if I were to want to do that I could change it back with a simple terminal command. If you go this route, remember that you will also have to remove the sleep image or it will still be there taking up space (8GB in my case). I think I'm most pleased with the fact that the computer doesn't vibrate anymore. I used to set my hand on the computer to tell if it was still on and cannot do that anymore. I like it. It also seems to run cooler than it did before but any evidence of this is merely anecdotal as I did not take temperature measurements before and after.
Overall: I'm pleased with the drive and hope that this will help my Macbook Pro last for a long time. I still keep backups of course but I feel better about having the SSD in there. Apple's prices for SSDs are ridiculous and I grabbed this drive for $199.99 off Amazon by watching dealnews.com and waiting for it to do down. I'm sure it will again; just keep an eye out. Keep in mind that if you have an SATA II interface it will only run at a maximum of those speeds rather than the SATA III speeds but this drive is compatible with both interfaces. Even with full disk encryption (FileVault 2) turned on, this is much faster than my old HDD.
UPDATE 9/17/12: Just wanted to update my review now that a few months have passed and OS X Mountain Lion has been released. I upgraded from Mac OS X 10.7 Lion to OS X 10.8 Mountain Lion through the App Store with no problems (and subsequently 10.8.1). Of note, after upgrading to 10.8.1 I was unable to access my Recovery Partition; holding "alt/option" and "R" at the same time would automatically jump to internet recovery mode. A reinstall of OS X Mountain Lion seemed to resolve this, though I am still unsure as to the cause.
Moreover, if you enabled TRIM support you will have to go back and re-enable it since every OS upgrade reverts back to having it disabled. The process also has changed slightly under OS X Mountain Lion 10.8 so make sure you follow the proper method should you choose to do this and be prepared to do this after every OS upgrade (i.e., 10.8.2 or 10.9). Again, also understand that doing so is not sanctioned by Apple and could result in major problems and perhaps even loss of data.
Furthermore, Carbon Copy Cloner is no longer a free application as it was when I first wrote my review; it now costs approximately $40.00 for a license; however, I believe you can try it fully functional for 30 days before buying. If all you need to do is clone your original HDD to this new SSD then it should still work just fine assuming you do it within 30 days of downloading Carbon Copy Cloner.
Lastly, I see that the drive is now $159.99 at the time of this writing. It was approximately $250 when I paid $199.99 for it. My recommendation of this SSD still stands, especially at that price. After several months of use it does not seem to have slowed down at all and has been nothing but stable.