Totally worth it. There's a lot of awesome sounds you get with, and can get separate, in Nexus.
I bought Nexus2 with the Hollywood 2 expansions ($250 just for those expansions), as well as the Dubstep/Electro Volume 3 expansion (Something like $60 if I recall)... and I think one more that I can't remember off the top of my head.
Overall, it cost me $600... But I don't regret it at all. Every time I play with it, I find a new sound I quite enjoy. I've found a lot of favorites in the Halloween expansion as well, which came free with the VST.