SageTV recently released version 5.0 of their software. I'm waiting for the current TV season to end to evaluate it, but I like what I saw so far.
One of my favorite tools on my HTPC is HIP. It's a freeware remote control manager like Girder... but free. You can make any remote control work with any piece of software on your machine. You can easily setup a harmony remote with your HTPC. I personally prefer to use PowerDVD to watch my DVDs. It support post-processing with ffdshow which makes a huge difference in quality. With HIP, I can call up, use and dismiss PowerDVD easily.
I'm currently using Beyond TV 4.2, but SnapStream has been in silence mode for the past few months about their future plans. With Meedio being bought out by Yahoo recently, some rumors about SS being snatched up soon as well are starting.
I'd use WindowsMCE 2005 if it could support 4 tuners, but it can't.