I don't know why it is generally enabled on "server" installations. That being said, the only time I've had a legit use of it was on a media server, running mediatomb, which uses avahi to do SSDP/mDNS/zeroconf/DNS-SD [1], and on the client running VLC (I think the "local network" options interface with avahi itself). Which actually ended up being quite nice. I usually disable it, and try to uninstall it completely, on other server installations.

[1] http://en.wikipedia.org/wiki/Zero_configuration_networking

I can't seem to install GVIM on Ubuntu without avahi. I wish I had more choice about it.

Try installing vim-gtk instead of vim-gnome.

IIRC, it would have required me to add the 'universe' repository.

try using Gen too the use flags allow for great flexibility and allow smaller packages.

It provides compatibility with Apple's more recent network technologies (Bonjour/Rendezvous etc), plus probably other stuff I don't know anything about.