It's pretty intense - Not unenjoyable to me because I love Coasters. It doesn't go upside down, but the backwards thru the mountain in the dark down spirally banked turns can be disconcerting. The first time, I was so disoriented in the dark, that it almost felt like we had gone upside down - You don't, but that's how surprising it feels.
To me, the Viper is nothing - ExEv is smoother, themed, faster - just all around better.
The only way you're going to know if you like it or not is to do it. It's a great attraction. I would encourage anyone to give it a shot who doesn't have motion issues or fear of drops (DH doesn't like drops) to try it.