I got the Philips DSSreceiver/TiVo combination unit a couple months ago, and it truly changes the way you watch TV. I wish I'd done it much sooner. I don't have experience with Ultimate or Replay, but I am happy with the features and functionality of TiVo, and wholeheartedly endorse SOME kind of PVR. The more video-based forums have areas dedicated to PVR's and even the individual brands/services. Email me if you want some suggested links.
Tim
Tim