Shai wrote his own colemak vim config and posted it here on these forums.  A quick search should find it.

Back when I used vim (I'm a sam user now, highly recommended), I used a slight modification of sykora's colemak vim config.  I like it since it's much more minimal that Shai's and the keybindings are much closer to the original vim ones.  There are some slight differences though, like using neio instead of hnei for navigation.  I think this makes sense, since your hand is already on these keys.  In fact, I liked it so much that I now use 'neio-style' keybindings for several other apps, such as dwm and surf.

My configs can be found here.

Since I use vi/vim at work on hundreds of servers, I cannot practically use any custom keybindings.  But the well-known standard ones work just fine for me with Colemak.

hjkl navigation could be a problem but I just use the arrow keys instead, or other movement commands (w, f, 0, $, ...).

Jrick: Vim isn't really so dependent on key placements! Most of the bindings are letter-mnemonic in nature, and therefore work just as well with Colemak as with QWERTY. The arrow key functions may be worth remapping, but I myself use the PKL Extend mode for that instead (in Windows).