Well, this kind of question will get you a lot of different answers but since I just bought a galaxy nexus on release day and since I am also planning on getting an evolte when its released I think I can asnwer your question. Now as far as specs goes there isn't any doubt that the evolte exceeds the gnex but this spec war in my opinion is getting out of hand. These companies really need to focus more on user experience/battery performance versus who has the most cores.
Anyway, there are other phones that have better specs(not by much) than the gnex but I hardly doubt you can find a phone thats any more responsive than the gnex. Everything I click on opens up instantaneously, there isn't any lag whatsoever when using this device. Some people may say to not waste an upgrade on a phone with last years specs but the gnex really is a great phone to own. The screen is beautiful to look at even though the pentile display gets on my nerves at times, especially on fine print but for the most part the display is great.
As far as the evolte, based on the one x reviews the screen(slcd 2) is the best screen on the market so far which is saying a lot and even though the camera may not be the absolute best smartphone camera it does have quite a bit of features that put many other smartphone cameras to shame. And then there is sense 4.0 which seems to be a lot less resource hungry and compliments android 4.0 versus trying to replace it. So to answer your question if you aren't entirely in a rush I would say just wait for the evolte but just know the gnex isn't a bad option either.