And keep in mind that the "lifetime" subscription (usually around $250) is only for the lifetime of the particular box its attached to. So if you buy a current Series2 TiVo with a lifetime subscription, and then upgrade to an HD model DirecTV DVR, your lifetime subscription won't apply to the new box.
(My personal opinion, and the reason I'm holding off on DVR, is that I think we should either buy or rent, not buy *and* rent. It's almost enough to make me dump DirecTV and go with TimeWarner Digital Cable. They treat the hardware and software as a service to rent, so a SciAtl 8000HD costs $0 up front instead of the $1K Hughes wants from me for their HD DVR *before* I even get the privledge of renting their DVR service for $10/mo or whatever.)