I intended to wait for newer models, but this product so directly fills a need that I couldn't wait any longer. The TiVo is outstanding and truely changes the way I watch TV. The software is great, and extremely easy. The unit integrates well with my hometheater (though I would like more inputs and outputs, especially S-video). Finally local cable channels and satellite are perfectly integrated. I didn't think I would, but I prefer the channel guide on the TiVo to the DirecTV style. Recording is so easy, I can't get over it. There are mony resources on line which go in to details and compare the two devices.
TiVo appears to have the momentum and better programming. The Phillips backing and retail availablity have given them the edge. ReplayTV was stronger out of the gate, but it appears TiVo will dominate. Of course, this technology will continue to evolve and ultimately will be integrated into other devices, but for now, it is worth every penny.
I recommend buy one now, and when new untis come out with improved hardware, put the original on another TV/system in the house. Once you've used one you will want one on every TV, at least I do.
Strong Recommendation for the TiVo (I suspect the Replay is equally awesome).