I live in Irvine now. As someone who did their undergraduate work in Santa Cruz, which is an amazing college town, and a fantastic place to live, I was a little disappointed with Irvine at first.
Irvine is, somewhat, as described by an earlier poster. I cant really put words what my initial impressions of Irvine were. You have very wealthy people from Balboa and Newport, the upper part of income bracket for suburban southern California, mixed with the college crowd. The actual area around the university, at first, didn't seem very college towny at all (it reminded me of UCSD a little). You certainly don't have the ambiance of Santa Cruz. There are only a few coffee shops, no real bars or pubs, no record stores, etc.
After a few week living here though, you'll find that there is a vibrant community. Most of the grad students live on campus, where there is a great community, and you'll discover that you can walk almost anywhere. You'll also discover a great art theatre, and some hidden gems.
Now having said ALL that you have to keep a number of things in mind. First Irvine is situated smack dab in between Los Angeles and San Diego. San Diego is about an hour and half drive, and LA varies depending on what part of LA you want to go to. You will find that you are WELL situated to be part of one of the best music scenes in the world. You can easily drive to great record stores, venues, all kinds of shit (pardon the language here). You'll also be 10 minutes away from Newport Beach, easy driving distance to all the beaches in San Diego and LA, 2 hours from the desert, 2 hours from the mountains...
And Irvine is also the "safest" city in the United States.
Is there a moral to the story? Well, I suppose I'd say that Santa Cruz is a better community, UCLA has a better "college community," but Irvine is at least as good as La Jolla (UCSD) and has more going for it than some seem to think.
Cheers