I just moved from AT&T to Sprint about a week ago and so far so good here in San Diego. AT&T 's speeds were great but being stuck with the 3gb of data and spending nearly $200/month for two lines was way too much. My bill is down to $136/month for two lines and there is LTE covering about 70% of the city so I can't complain. It's fast enough for my mobile work. I do hope that the coverage continues to expand down here though.
I do admit when I do hit 3G it does suck even though it isn't too often that I do.
The speedtests taken there are at my job. I hit between 15-20mb where I live.