well, I guess I'm the only one who has a Replay over a Tivo. It all depends on what's cheaper and what you want to use it for. They're essentially, (at this point) the same thing. If you're REALLY going to get a 50xx series then you'll hve the built-in commercial skip feature which I believe was eliminated in subsequent models.
I got the replay over Tivo because I'm a hobby-aholic and was able to hook it up to my LAN, offload the mpeg's to my PC and archive them off to DVD. The Ulead DVD burning program allows me to create my own menus and everything.
The real place to browse around and search to find answers to your questions would be at avsforums.com
-=Fair warning=- Some members go ballistic if you ask a question that's been answered a lot, so do a search.
If I can help answer any user interface questions you may have don't hesitate to write me at
djheater hotmail.com