I do not think my tweaks speedup the startup of nexuiz.. Sounds like some issue with compiling the shaders to me. Willis said something about a fix for this in 1.5.1. I myself never had problems with a long startup time so i have no idea if this does indeed help.
I think there are still some issues with the current 1.5.1 release candidate but you might try to download it and see if it does start faster then the current 1.5 version. It is also interesting to get a mac user to test this. But please notice its a release candidate some things might be broken (please report them here). And you will also NOT be able to join the online servers because of the version check. But a quick local try with 'instant action' or 'create game' should work fine..
Here you can download it:
http://sourceforge.net/project/showfile ... _id=183317