Fuzzy,
I started out with the Snapstream Personal Video Station software about 8 months ago or so. I used the application nearly daily and was relatively happy with it. Recently, Snapstream software renamed the product to 'BeyondTV'. This upgrade has significant improvements over the earlier product, while retaining the very-professional interface. I have not used SageTV, but would strongly recommend that you check out the demo of BeyondTV. It will easily do everything you are looking for.
By the way, the guy who mentioned the PVR250 failed to mention that you have to wait for the entire show being recorded to complete before watching the show. With BeyondTV and software decoding, you can being watching your show while the remainder still records. This is great when you want to watch a one hour show but skip the commercials and still end when the show ends. For instance, I watch West West every week. I start watching it around 9:15 or so. I start at the beginning, while the rest of the episode is recording in the background. By fast forwarding through commercials, I finish at 10:00 and can go to bed. With the PVR250, you would have to wait until 10:00 to watch your show. That limitation annoys me. Assuming you are using a dedicated HTPC, I wouldn't worry too much about hardware decoding by the capture card. The other point to make is that the PVR250 is an expensive card compared to the myriad of other options. And if you don't have that specific card, you can forget about SageTV.
BeyondTV offers much more hardware compatibility and allows great PVR functionality. I also own 2 ReplayTV units, a 3000 series and a 5000 series. Although they offer some benefits in terms of being a turn-key set-top-box solution, you have the monthly subscription to worry about. And the lifetime subscription is very expensive.
For those who don't know, BeyondTV has now included a feature called 'SmartSkip'. When you're watching a TV show and a commercial comes on, all you have to do is hit the channel-up button and you will automatically skip all the commercials and return to your show. Not quite as nice as the Replay 5040, which does this on-the-fly, but still better than manually forwarding or skipping 30 seconds at a time.
Do yourself a favor and at least try their demo.
HTBuilder