DirecTV is switching to MPEG4 in just a few months for it's HD channels. So, any HD receiver you get right now will not work in a few months....bummer!!! No word on the upgrade path if you buy one. My guess is they'll force you to sign a 1 or 2 year contract to upgrade to a new MPEG4 HD DVR.
Are you sure you even have a choice right now? I thought the ONLY DirecTV HD DVR is the HD Tivo which is $999...way, way overpriced! Especially when it'll be useless in a couple months.
My advice, if you have comcast cable, switch to them. I just did and I love it. I get an HD DVR for only $10/month, all my local channels in HD, ESPN HD, Discovery HD, INHD1, INHD2, HBO HD, a $20/month discount for an entire year for switching from DirecTV, a $10/month discount on my high speed internet. I'm paying less than I was with DirecTV and now I have tons of HD, an HD DVR, HBO, none of which I had with DirecTV. Plus, comcast and Tivo just announced a partnership...comcast Tivo's in 2006, yeah baby! Life is good!