My first thought was how amazingly small the unit was. I suppose it's basically just a PCI card combined with some usb circuitry, but from the pictures on the Amazon site, I assumed it was the size of a desktop PC. The photo to the right is the unit in the palm of my hand.
The signal strength was great, though my base station is only about 30 feet from the TiVo, with no obstructions (second story loft down to the first floor). It doesn't require a power adapter which is great (my outlets are already crowded with gadgets), drawing power from the usb connection. It plugged in, grabbed an IP, and has worked fine ever since. I think it's going to be one of those set-it-and-forget-it kinds of products (the kind I love — they don't require futzing around every so often).
The biggest and only drawback to this in regards to a TiVo is that you must have the 4.0 TiVo OS in order to use it (which requires a Series 2 box as well — Series 1 owners can use a slightly more hacky TiVo Airnet from 9thTee). If not, you'll run into the problem I had, where you'll have to use a phone-line (or usb-to-ethernet if you have the 3.2 OS) to force an update to the latest OS before it will function.
Once the setup was complete, the unit has worked flawlessly, it's small, fairly cheap (40 bucks after rebates), and I'll be getting updates every 30 minutes or so from TiVo, all without ever needing a phone line again.