Not bad at all. I'm actually very happy I got mine. The difference in speed alone was well worth the update. Especially considering it didn't cost me a penny after selling my 4s.
I'm at work today and the performance compared to my 4s is great. Not sure if it's the LTE, but I no longer have to position it just so on my desk to get a signal. Almost left AT&T because of the horrible coverage at my job, but switching phones made a world of difference.