I have a dual 1.7G Xeon with 1GB of RAM running Gentoo, and the performance is fine. I actually find it more stable than the linux version, which has this annoying bug - If you search for a word and it is not found in the document, reader crashes. This has been reported by many people on the adobe forums, but they have not fixed it. So running the windows reader is nice. Also a lot of new files including the latest Lessig book require reader > 6.0.
The interesting problem I now face is that checking for online updates crashes the reader. I had to do a new install of cxoffice, and this is a new problem that surfaced. This used to work before:( So if that is the case for other as well, disable the automatic checking of online updates in the preferences.
Naren