When you upgrade your TiVo, you lose everything.
Season passes, wish lists, saved thumb ratings, channel configurations — everything. Yes, you can transfer recordings — but only one at a time. It’s a very slow, very manual process.
What TiVo needs is a migration assistant. When you get a new Mac, the Mac OS X setup assistant automagically copies over your applications, network settings, files, user account, password.
After you’ve migrated everything, you log in to your new Mac, just like it was your old Mac. You don’t notice a difference. Just that it’s faster.