LTE just went live in the Quad City (IL/IA) yesterday morning, so I've naturally been thoroughly testing it out. I'm averaging about 10 mbps down and 4-5 mbps up, but I've had peaks well above 20 mbps and valleys as low as 5 mbps. Strangely, there doesn't appear to be a direct correlation between speed and number of bars of reception. There are times when I have only a bar or two of reception and still get well over 10+ mbps. And there have been times when I have 3-4 bars only get around 5. Generally speaking, though, usually the more bars the faster the speed, but not always (not sure why).
Also, my first speed test with the app usually seems to be slower than subsequent ones. For example, my first speed test might be 5-7 mbps down, but if I run it again, it'll bump up to 15-20. Not sure if that's just a natural ramp-up of the radio or what?