I was in a similar position. I didn't really want to invest in a lot of equipment knowing that I'd want the HD Tivo as soon as it was available. The cheapest solution from an out-of-pocket perspective was to get some HD channels via cable from Comcast... they will lease me an HD cable box for $5/month. I already get basic programming from them, simply because I have cable internet access, and it's almost as cheap to have basic cable + cable internet as it is to have cable internet as a non-cable subscriber. So for $5/month, I would have at least gotten some local network feeds in HD. But to get things like HBO, etc., in HD, I would have had to up my package with Comcast (and therefore drop the packages with DirecTV).
So I was just honest with DirecTV. Told them I could get into HD with comcast for $5/month, while staying them would have been a sizable investment in equipment. I told them I wanted to know upfront if there was anything they could offer that was more competitive with cable BEFORE I ordered cable and dropped them. I was switched to the customer retention department, and of course was given the "we don't do this for everyone, but since you've been a good customer for so long....". Basically, they offered me the $399 HD upgrade package & install plus $50 for a phase 3 dish, BUT they paid for half of it in the form of a credit. So for $225, I got a box that is capable of receiving HD from both DirecTV and OTA, plus the necessary dish. That was acceptable to me, as I should easily be able to sell it for at least that much when the HD Tivos come out, so I'm not really paying anything extra to enjoy HD in the interim (except their programming charge for HDnet, etc.).
