In our video below, the ThunderBolt got download speeds between 5-7 Mbps, though occasionally throughout the day we would see download speeds up to 10-12 Mbps. So it does appear the time of day may matter, as well as how many people are connected in your area using the network. What's puzzling is that the upload speeds would be between 30-40 Mbps, so we can only guess this must be someone weird going on with the SpeedTest.net program, or with the network.
For comparison, we did the same speed tests using the same servers and got 1.32 Mbps download and 0.67 Mbps upload on the Motorola DROID X, and on the iPhone 4 it was even less at 0.68 Mbps download and 0.43 Mbps upload.
Naturally, all these results would vary due to different locations, so your results may be different, but it is clear that Verizon's 4G LTE network is providing a much faster data connection than its 3G EVDO Rev A network.
The ThunderBolt has a feature called Internet Connection Mode, where you can connect the phone to your PC via the USB cable and use Verizon's 4G LTE network as the PC's internet source. When we did this with our PC, we were able to run the standard SpeedTest.net web site in our browser (FireFox) and got a download speed of 11.53 Mbps and an upload speed of 6.50 Mbps with a Ping time of 79 ms using the closest server (Miami). We then did the same test using the LG VL600 4G USB Modem connected to our PC, and got a download speed of 10.61 Mbps and an upload speed of 6.48 Mbps with a Ping time of 84 ms. So based on these results, it appears that in our area (Ft Lauderdale) that both the ThunderBolt and LG VL600 Modem are capable of the same speeds on average.