Here's another item that while it is better than its competitors is it worth the extra cost?
Sigma no longer makes the 70-200mm f2.8 without stabilization, and there version with lens stabilzation is $1400, and I don't belive that has any value for us Sony users. I do not have any empircal evidence that lens stabilzation adds nothing when you have body stabilzation since I was unable to find anything written on this, and from a technical viewpoint it wouldn't make sense that they could work together in reduce vibration even further from in-body stabilzation.
So the Sigma with stabilzation cost twice as much as the old version, $1400 and has driven the old models in the used market to over $1000.
The Tamron is still very affordable at less than $800, but suffers from very slow focusing speeds. The optics test-out on par with the Sony lens and are superior to the Sigma. The Sigma's are fast, but suffer in optical peformance.
So one can easily argue that to get a 70-200mm f2.8 without any significant limitations one must go with the $2000 Sony lens, and several reviewers have posted comments to that extent. As with other pro quality equipment, its not of value to you if you are not going to be utilizing those features. So if you are really just going to be shooting portraits (or anything where autofocus is not critical), then the Tamron is an excellent choice. The Sigma is not an option new because I don't think it makes sense to purchase features that you cannot use. Look for the old Sigma in the used market, should be able to get a used model on Ebay for less than $900.
The Sony does have some features the others do not. There's an extra button that can double as a focus button or a DOF preview (if camera supports). I have an a580 and its supported and the DOF preview is quite slick; gives you a preview of what the background will look like at the current selected settings. Saves taking a setup shot and checking the screen.
Focusing is faster than the others, but is slow at low light (like most). Images are crisp and colors are excellent. Focus on the edges may not be as good as the Sigma or Tamron. All-around the lens has no signifcant weaknesses, and that's saying something. For us Sony owners you will not be able to bring a better tool, no question. Weight, could be an issue for many of you. All reviews of telephoto lenses say the lens is heavy, but this lens is a beast! It weighs more than my old 100-300 mm sigma lens, with 100 mm lens focal length. Obviously, its built like a tank as well, so take that for what its worth.
Question is it worth the extra $$'s??? I'm tempted to say "No" for most people, except me:) I only carry a few lenses and I want each of them to be the best I can carry in each class because I only have a few lenses. I used to carrry a Sigma 100-300 f4.0, and I found the lens to be less perferred for shooting video, I wanted something faster and shorter. If you do mostly outdoor then I think there are much more versatile lenses out there, like the Sony 70-400mm, where the extra speed is really of little consequence. I do a lot indoors without flash and this lens does rock for those applications, and now that I have this fast beast I can put converters on it and it will perform well, so it is very versatile in that regard.
It is the best 70-200mm f2.8 lens for a Sony DSLR camera, no question. The question is, is the extra cash worth it, and in all the cases where I've spent more money instead of being frugal, this is the hardest one to justify because the delta is just so enormous. If the lens were $500 cheaper, I'd easily recommend, but at the steep cost to ownership where this lens currently resides......
******* Review Updated*******************************
7/1/12
I was afforded the opportunity to use a Sigma 70-200mm F2.8 lens for a few weeks from a friend of mine, so I was able to make direct comparisons. Please look at the photos that I attached of each shot, trying to duplicate the same shots.
The biggest thing I noticed is that the focusing system of the Sony is far superior. I took some action shots and the Sony lens could rip off twice the number of pictures it seemed when asking it to re-focus between each shot. Also, notice the shots I took that tested it's focusing ability and the Sony just flat shinned. One image I took of a box with lettering and the background exposed and the Sigma could not lock, where the Sony immediately locked. The image of aloe vera lotion however was the most interesting shot; the image was a difficult shot to be able to focus on because the lotion bottle is clear and lotion is translucent as well, and then the back ground was very bright. Very difficult focusing task, and the Sony Shinned. The Sigma did lock, but you see for yourself that the image quality was poor on the bottle itself. I think the colors on the Sigma are good (if you like them warmer), and the bokah was slightly better where the Sony was a touch more harsh. However, the colors could be post processed into the image, so that's a non-factor, and the bokah of the Sigma was just a touch better on the Sigma.
The feel of the Sigma lens was impressive. The all black look, and solid feel was just as good as the Sony. The Sony lens looks like a Pro lens because of the "white" factor, but if I didn't know better I would say the Sigma looked better.
So from a performance perspective my testing clearly showed that the Sony is certainly better than the Sigma in nearly every way, and in some cases significantly better. I was told and read the Sigma would perform up with the Sigma from a speed and focusing ability, and clearly it could not. I'll update this review if I ever get a chance to compare the Tamron head-to-head, but from this review I cannot even recommend the Sigma lens at all. The Sigma I tested did not have the stabilization, and if they have not dramatically improved performance the $1400 for the new lens is a bust for sure! The only question remains is can the Tamron optically perform up with the Sony like people say it can for 1/3 the price, that's the only reason I leave my review at 4 stars because let's face it, my Sony copy destroyed the Sigma copy I tested.