Jim poked me on AVS to post a wishlist for MC's TV/DVR functionality, which is probably good because I keep meaning to give it's functionality a shot. Below are, in chronological to when I notice them or basically no particular order, my thoughts/wishlist for the DVR functionality in MC, as it stands today. Full disclosure, I've been using SageTV since version 1.4 or so, so I've got a bit of a bias about how I expect things to work so that will probably factor in here. So, onto the list.
I don't see a way to enable/disable which tuners MC uses. In the TV section they are all automatically listed whether I've configured a tuner or not. This worries me to a degree because I sometimes (often?) have a tuner that is not properly setup or not compatible that is listed here. Case in point, in setting up MC today I see both my HDHR and my HDHR Prime (w/ CableCard installed). Now as I understand it, MC doesn't support the Prime so I don't want the Prime configured or used, but I see no way to prevent it from being used.
I'm just going to toss this out here: Extenders. I don't want to have to build a PC for each location I want TV, heck I don't really want a PC at any location I want TV. For my music at home I use a Squeezebox and a Roku (the old M500-audio only version), for my TV I currently use SageTV extenders everywhere. Extenders were the single best thing I ever did to my system, they improved reliability and quality (native output switching, smoother decoding, etc).
Setup from inside a 10' UI. I run my systems from a headless server, so it's "difficult" (OK not really but it is more of a pain) if I have to remote into the box to configure things like channel lineups.
I'll be back edit this some more, but I'm out of free time for now so I'm going to post it so my (still incomplete) thoughts aren't lost.