OK, as someone who has had one since 1/2004, a few observations.......
1. The picture is amazing. I migrated from a 721 and even SD programming looks better when upconverted. I watch mine on 1080i through the DVI port on my Sony RPTV (KP57WV600). Watching Smallville on HDNet or one of the HD camera programs on DiscoveryHD is awe inspiring (Watch the HD Demo channel when you first get it hooked up.... assuming you haven'tused a 5000/6000 or 811 and are jaded re: HD pictures. When I had hooked mine up it was the first HD pictures I had seen in my room.
2. "Doctor. it hurts when I do this......" "Then don't DO that".
OK, if you want to try and trip up the 921 you can do so. Most of us engage in this behavior when we get a new download and we want to see if the old vulnerabilities still remain. An Example.... Setting up two HD timers for 8pm, another for 9pm, AND watching a recorded program, while jumping back and forth, etc..... these things quickly max out the resources of this glorified PC and invite crashes and glitches. In a perfect world, it work out of the box, but it is not as stable as we wish it to be. Compared to the Grey Screen of Death lockups that happened daily for some people, the system is much more stable. As stable as a Tivo? No. But if you are locked into E* for whatever reason (Superstations, Grandfathered Distants, etc.) this is the best there is for now, as far as HD Capability. The 942 will be DOA in that it is not compatible with Mpeg4, and it has only one HD tuner onboard for $200 MORE than the 921 is selling for right now.
3. I have about 20 active timers a week and on average I get a glitch once or twice a month, usually of the ZSR variety on CBS-HD when King of Queens airs. It used to happen on HDNet when I was taping Odyssey 5 at 2am as well, but has not hit me when Smallville is on. The failure rate is NOWHERE near as bad as the Dishplayer had during its infamous trouble period 3-4 years ago. I've got 2 SW64s feeding 5 receivers, so my setup is fairly complex and might be inviting the problem during random times.
4. You are already in good shape by being here as the CSRs are clueless in most cases and try to imply that the problem is on YOUR end when glitches occur. Always ask for an advanced tech as soon as you get through to save yourself some headaches dealing with the CSRs.
5. In the "an apple a day" vein, I recommend buying a UPS to feed clean power to the unit, and give you an easy on/off button to do regular hard power resets, which I do twice a week. Regularly check your timers list to make sure they are lined up in the order they are scheduled to fire. If they are not, do a hard power reboot. This will usually keep the bug away that causes the wrong program title to be listed (it is usually the program that was on directly BEFORE your recorded program. Not a major bug, but it makes it hard to easily find your programs if you have a lot of them)
6. If the remote isn't responsive for a sec, DON'T keep hitting buttons. Some of these glitches go away after a few seconds. Wait 10 seconds and try moving the direction key to the right until you see one of the buttons highlighted, then do what you want. Don't forget to swap out the batteres at the first hint of trouble as well to eliminate that as a problem.
7. Set reasonable expectations (think Microsoft..... I expect my computer to crash once a while, so I'm not too upset when it does). When glitches occur, a hard pwer reboot usually brings it back fairly quick. If this DOESN'T cure a problem. Try unplugging the antenna feeds (tuner 1 and 2) and reverse them and then run the check switch again. One time, I got stuck with a tech trying to fix a nasty bug (I couldn't get a picture at all, but the menu was coming up) and this cured it instantly. Something about forcing the reinitializing of the tuners that made the bugs go away.
I've only had to call E* about 5 times about this unit and I am still using one of the originals that has the firewire ports still on the back of the unit. If ANY machine should have problems it should be me. Yes, it would be "nice" if E* could get their act together. In the meantime $550 buys you an HD PVR with two HD tuners, an OTA HD/SD tuner, 180 hrs of SD (25 hrs. of HD) recording, and HD pictures in all their glory. Not a bad deal, even if it is only for 1-2 years while they bring Mpeg4 online.
If you are NOT tethered to E*, then D*'s upcoming HD offerings might be more "compelling" (to steal Charlie's word) in the mid term. V*s could be as well, if you can wait for their PVR, scheduled to arrive in March (assuming Cablevision hasn't pulled the plug by then - I can't see how much longer Cablevision can afford to lose $50 million+ a MONTH on this service).
The 921 can be aggravating at times, but the unit can also be a joy to use, WHEN it is working without a glitch. You just have to get past the greyed out Internet and DVhs setup menus that tease you about what might have been as do the memories of that Keyboard with the remote buttons they teased us with a year ago that never materialized (JUST Like the 721).