Good idea.

DirecTV has more HD than anyone at the moment, and has exclusive rights to MLB Extra Innings and NFL Sunday Ticket if you like football and/or baseball.
I've had DirecTV since 1995 and I've yet to have a problem that required an unscheduled DirecTV visit. The initial installation and setup will be included when you first sign up for service, and since you're leasing equipment, if any of that goes bad you just call DirecTV for a replacement.
As far as overall stability, in 12 years I had the picture go out one time for 5 minutes. I'll take 99.999% uptime.

Rain fade really isn't an issue (even when it does rain my picture never goes out).
I wouldn't bother with the warranty. It would only be for unscheduled service on your lines. Equipment is leased so that wouldn't apply. They'd ship you new equipment if you ever needed it, and you can do all of that work yourself.
I would try negotiating that down when you call. Just tell them you're considering switching from cable but the $199 startup fee for equipment is too expensive. They'll wheel and deal with you to get you to switch. They'll make you commit to DirecTV service for 2 years minimum, but for that you should be able to swing a good deal - many have reported they were able to get the equipment for $89, $49 or even free depending on the situation.
TimeWarner has to add programming nationally, and they have a far more complex infrastructure in place than DirecTV does. I certainly would not expect them to add as much HD as satellite has right away - they have analog channels that are taking up a LOT of programming bandwidth at the moment.
The DirecTV HD DVR's have become quite sophisticated with a myriad of software updates they've released over the last year (they used to be crap - Tivo's were the way to go but their DVR's have finally caught up with Tivo functionality and then some). You can add on as much hard drive space as you'd like with an external ESATA drive (the built-in drive holds close to 30 hours of HD programming and 200-300 hours of SD programming as it is since most of the new HD channels use MPEG4 compression). If you want more space though, that is an option. They all have dual-tuners so you can record two shows at the same time while watching a 3rd recorded program.
They also now have DirecTV Video on Demand - it allows you to download shows you want to watch for free (95% of the shows are free) over your internet connection.
As far as HD content - They'll have about 15 more regional sports networks available nationwide in HD by mid-November, which will boost their national HD channel # to over 85. They plan to offer up to 100 by the end of this year.
They're also launching a new satellite in Q1 2008 which will give them more SD capacity.
- T