I've had my DHG-HDD500 for about a week. We subscribe to Comcast here in SF. Sorry, I didn't get a good look at the cablecard before Comcast installed it. I've got it hooked up to my Sony TV via HDMI.
PQ: Like most folks who have posted here, I think the PQ on this is fantastic. I can't see any difference between the PQ using this unit and the PQ when I piped the picture directly into my TV. (On my old Replay, the compression was painfully obvious.)
TVG: The guide has slowly filled in, with blocks of listings missing for night programming at Day +7. I'm hoping that eventually I'll have full listings for 8 days but I'm not there yet. The descriptions are somewhat less full than Replay's and the navigation is less intuitive (I seem to hit Select when I should hit Menu, and vice versa).
Recording Interface: OK, the software is less robust than my old Replay's. No ability to search program descriptions (need to review all Baseball listings rather than searching for "San Francisco Giants"). As others have noted, no ability to set up "Channels" or "Favorites" that record based on themes. One does have the ability to search for programs based on category (e.g.. HDTV programs) but it's often incomplete (HBO's HDTV programming is not listed).
Although there is no ability to group recorded shows by subject matter once you've recorded them, the list of recorded programs is well-organized. Yes, it took me a while to figure out that the manual's instructions on how to play recorded programs is just flat wrong but once I did, I found Sony's system easy to use. (For example, every Seinfeld episode I record is kept in the same place, regardless of when I taped it or from which network.)
Most people won't care but I used to record DVDs from Netflix on to my Replay hardrive through component inputs for later watching. But the HDD-500 only has a cable input.
Reliability: Where the rubber meets the road, and I'm sorry to say I've encountered problems. I've had a couple of programs fail to record, one on TCM and one HBO. I've actually been watching while this happens. The unit tunes to the correct channel, starts to record and then stops within a second or two. This has me baffled. I've reviewed the "Recording History" (hey, good for Sony for including this) and it gives me an error message "Recording not permitted by service provider." I've then tried setting it to record the program using the record button on the remote but the red "record" dot on the listing disappears after a second and nothing happens. The only "solution" I've found is to unplug the unit.
My Replay was not 100% reliable, but it was usually a tuning issue between it and the cable box. Anyone else encounter this? I almost wonder whether this is a DRM issue (my wife warned me about buying hardware from a content provider, I hope she's wrong about this).
Remote: OK this is minor, but a mute button would have been nice. The scroll wheel was a little mystifying at first but it's growing on me. Ablity to program to ff 30 seconds is nice, but I miss Commercial Advance.
With the exception of the missed programs, I'm generally pleased with the unit. But I think Sony still has work to do, and the lack of an internet connection (not to mention the disabled USB port) leads me to conclude that Sony doesn't plan to upgrade software on these units. Hope I'm wrong.
Anyway, I'm think I'm going to stick with this for now. The PQ makes up for things I wish Sony had done differently. Have I mentioned it's fantastic? My feelings may change, however, the first time I get the "Recording not permitted" message instead of a program I actually care about.