I'm keeping mine (got 30-plus disks). I actually have TWO HD-DVD players now, one of which doubles as a HD DVR, plus the 360 add-on. One is in the living room, the other is in my game room. I'll keep using the 360 add-on for DVDs and stuff anyway.
The logic here is that re-buying this stuff on Blu-Ray is not going to make it look better, just cost more, and that Blu-Ray isn't going to be around forever either. HD-DVDs will continue to look and sound awesome and I'll get hundreds of hours of enjoyment out of them. In 10 years, we'll all be making 'oh god MY EYES' jokes about Blu-Ray too, and raving about the new 10TB Blade Runner Ultimate Edition download on iTunes.
To be honest, i'm more pissed at the shelf space lost to DVDs. HD-DVDs won't be 'obsolete' in terms of video quality for quite a few years at least; DVD was sub-standard from the get-go. It's looking like a PS3 purchase is in my near future though, which kind of sucks 'cause i'm all out of space to put it and it doesn't do a damn thing that the 360 doesn't. Other than cure cancer.