Yep, ServU rulez
I used ServU for a while now and there are only two bad things I can say about it. First thing is that it seems to handle reverse lookups incorrect (that is, when restricting access on hostname instead of IP address it fails to lookup the IP address of the given hostname) witch makes restricting access a bit more difficult. Nobody seems to have the answer to this.
The other thing is a rumour that I couldn't confirm myself. The rumour says that ServU isn't handling bandwitdh good, and wastes bandwidth compared to other FTP server programs. I've compared ServU myself (to Bullet and MSFTP) with one large files and with many small files and in all case the I didn't detect any difference (except for MSFTP).
Cheers!