The HTC Thunderbolt has been overclocked up to 1.8GHz. It was enabled by twitter user @drod2169 who managed to create a new kernal. new kernal could be configured to increase the speeds from the regular amount which is 1GHz, to almost double the speed.
one interesting thing is that the effect that the clock increase has when benchmarking the smartphone. To see the graph, check out the image below. At the top of the list called “Your device:” is the Thunderbolt which scored an impressive 2772.