Using the Linpack benchmarking tools, Android 2.2 (Froyo) scored 37.5 MFLOPS. The same Nexus One running Android 2.1-update1 (Eclair) scores 6.5 - 7 MFLOPS. While obviously a benchmark, and not real-world subjective testing, which often differs, it would be a 450 percent increase in speed.
The Nexus One is confirmed to be getting the 2.2 upgrade, though its unclear exactly which other devices will get it. 2.2 also includes Flash, and you can watch a demo of Flash on the Nexus One below, by Adobe evangelist Ryan Stewart. You'll also spy an updated launcher, Android tutorial, and global search box.