Part of this problem is that TiVo, in their infinite wisdom, only enabled USB1.1 drivers on all of the TiVo boxes. Thus, even with a wired connection, you can't exceed 12 Mbps (1.5MB/sec) transfer to your desktop.

However, TiVo did actually include USB 2.0 drivers on most Series 2 boxes (if your Tivo service number starts with a 2, you should have USB 2.0 hardware). If you're enterprising enough to figure out how to get shell access on your box (it can be done in less than 30 minutes, unless you have one of the new "nightlight" boxes), you can get faster. I can extract video from my box at around 2.5 MB/sec (at that point, it's more a limitation of the TiVo's processor power) - but I'm also using third party tools, as opposed to T2G, since I've got one of the DVD-burning TiVos (Pioneer DVR-810H) that doesn't support transfers yet. The best I've heard of has been 3.0 MB/sec under ideal conditions.

If you're not so enterprising, TiVo's probably going to enable USB 2.0 at some point this year in an update (it's as simple as changing *one line* in the startup scripts).