I bought one of these a few weeks ago and have been waiting for Amazon to 'release' it so I could comment on it. Initially there were some known issues such as macroblocking/pixelation on digital channels (particularly channels showing HD content) with cablecards, but TiVo worked quickly to release two revisions to the TiVo HD software already and 98% of the issues have been resolved. My only complaints about the TiVo HD:
1.) Internal HDD only records 20 hours of HD content. It is equipped with an eSATA port, but as of now it is not enabled on the THD. (The Series3 HD has the eSATA port enabled, TiVo expects to enable it later in the year, possibly at the same time as a TiVo-branded eSATA HDD) 20 hours is ok if all you're recording is a day's worth of shows and watching through them daily, but I sometimes go up to a week without being able to watch shows, and if you record a few movies in HD, it fills up quick. Also on season passes the minimum you can set for programs to keep is 5, with the smaller hard drive it'd be nice if you could set it to 1 for things like news broadcasts (to set it to record daily and just delete yesterdays if you didn't get to it when it records todays)
2.) No built-in WiFi. I know the story is the same as Microsoft's "technology changes so quickly so adding in a wireless-g compliant adapter would limit it if a wireless-n standard comes along." but come on now, I hate having to add a bunch of items to the box, I'd rather it be built in.
3.) Basic remote. The Series3 comes with a glow remote and this one does not. You can buy a white or black one from TiVo for $50, but it is the newest TiVo DVR, they could include the better glow remote.
4.) No TiVo-To-Go or Multiple room viewing. Not so important on the MRV for me since I sold my Series2 to help pay for my THD, but I can see how this bothers people with 3-4 TiVos. I can appreciate that HD content is much larger and would probably take forever to transfer and take an enormous amount of hard drive space, but I liked transfering recordings to my laptop and taking them to my girlfriend's place who doesn't have cable or TV reception and catch her up on CSI etc. Rumor says it'll be enabled eventually, and I can at least appreciate that they put it on the back burner to fix release issues like the pixelation/cablecard issues.
5.) Menus, searching for programs, scheduling recordings, etc all do take a little longer than on my Series2. I'm hoping this goes away with a software fix soon. Hitting the 'record' button takes 10-15 seconds to start recording the show. (even though it still caches 30 mins of live recording and it does keep all of it, but one would think it could process the request faster)
6.) For the cost of TiVo service, one would think the software would have been completely release-worthy. On some of the forums, people have been complaining of issues with cablecards etc for a month and I think the least TiVo could do is give a few months free service to anyone who buys a TiVo HD so we don't feel like we're paying full price to be beta testers. Also, since it is a monthly fee, I don't think we should be subject to any sort of menu advertising. The guide is still ad-free, but in the menu, there is still a selection that can be any number of things (right now it is an option to learn more about the TiVo HD, but I've seen it be an ad for GM trucks etc) and one time when a program finished and it brought up the screen to choose between deleting the program or keeping it, there was a 3rd option to learn more about some program sponsor. This was one of the things that pissed me off about cable companies cable boxes.
All in all, despite the quirks, the picture is amazing and I'm glad I get to have HD content on my TiVo. I work swing shift and always miss all the good prime time shows and once I got an HDTV, the only show on in HD when I get home is Late Night with Conan O'Brien, and now when I get home I get to see all of my favorite shows in HD and commercial free. Life is easy again. Now if only I could add a 750GB eSATA drive, I can go back to storing large quantities of programs I may never get to watching. :) Nobody even comes close to TiVo, and the cable company's DVRs are all lousy.