1) Look at http://www.tivo.com/adapters first! Whoops? You're the type that always skips step 1, aren't you?
2) Believe it or not, they really mean it...the Linksys USB200M with firmware version 2 will not work. Exercise for the reader: Explain to a salesdroid that there are two versions of what looks to them like the same product. Get them to bring them all out. Find all are the dreaded ver2. Note that this is the only model they carry of wired USB Ethernet adapter. Move on to next retail establishment. Rinse, lather, repeat.
3) Finally find a store that does not have the USB200M, but does carry the USB100M--decide that "Not tested but reported to work" is a darn sight better than "incompatible."
4) Take home, plug in, observe cheerful link light. Go.