If you can separate the art from the artist (who has quite the fragile ego and thus defends it with insults), you can try Unreal Evolution by using a separate install specifically for it. Just install Unreal, then copy the whole Unreal folder, and use that copy for the mod.
Since the author is not very good at Unreal modding, coming from a Deus Ex background, he resorted to hacking the internal files of the game itself, as well as the original maps, to change them to his liking. This destroys a normal Unreal install, and affects any other mods you install on it, hence a separate one is required.
So long as you quarantine it away from your "legitimate" Unreal install, you'll be fine.
By the way, if you have UT99, you may also enjoy the freshly updated The Vale: Evelyn, which might well be the best single map created for Unreal to date.
And if you want to get the most out of your Unreal and UT installs, don't forget to install and use the HD Skins Mutator and HD Texture pack!
I think I will try as you advised and do a quarantine install.. The worst that can happen is i'll realise by ~Depths of Rrajigar that it's not for me and I can start again with the vanilla install. Will definitely try HD textures.
Oooh, the Vale looks pretty! I can install UT99 and Oldskool- I will aim to play things like Operation Na Pali and stuff eventually as well.