The DirecTivo fourm is probably a recommended read. There does seem to be a few problems to watch for such as defective remotes which RB has said Tivo/Philips acknowledge and will send out free replacements for when they're available.
But most people seem happy with them. The DirecTivos only recording quality ("perfect", since it's a stored copy of the digital satellite signal) gives you ~35 hours of video thats better than Replays or standalone Tivos "best", at which even a 60 hour Replay would only give you 20 hours. Plus the DTivo does DD 5.1 and has PPV listings which neither Replay nor Tivo standalones do.
But most people seem happy with them. The DirecTivos only recording quality ("perfect", since it's a stored copy of the digital satellite signal) gives you ~35 hours of video thats better than Replays or standalone Tivos "best", at which even a 60 hour Replay would only give you 20 hours. Plus the DTivo does DD 5.1 and has PPV listings which neither Replay nor Tivo standalones do.