I've noticed this as well. When I first got my Thunderbolt I was getting 15-30Mbps download, and incredible upload speeds. Even when Speedtest had their app updated, I was still getting the same upload speeds. Now, I get anywhere from 3-13Mbps download (usually between 3-7 though). My friend has the Nexus and when side by side, mine gets around 7-10 and his got 20-35. There have been plenty of times even though I have a decent 4G signal, anything I do such as web browsing, market downloads, etc., is extremely slow.