TweakTown posted a SSD performance comparison between Windows 7 BETA and Windows Vista SP1:

Today we have provided a quick and simple look at SSD performance in Windows 7 BETA and Vista SP1. It is far from conclusive, we know, but it was only designed to be a quick look at the numbers so far and what users may be able to expect from a standard desktop system. Based on our testing, we can see that obviously Microsoft have spent some time improving SSD performance under Windows 7, as it managed to beat out Vista in all but one test and that might have only been a slip up. Access time is also very impressive under W7 and when it came to CPU usage, W7 blew Vista to pieces scoring -1% usage under every test. Again, this might be a reporting error; but if it was, the results were very consistent