Ars Technica just posted an incredibly lengthy (40,000 words) article covering the history of Android.
It's quite an interesting read if you care to learn more about the OS itself and the differences between versions.
Assuming you've got the time I recommend checking it out, if nothing more than for interest's sake and seeing where Android has been and come from and maybe a likely idea of where it's going.
The really good stuff started happening with Ice Cream Sandwich (Android 4.0) and has continued on since then through Jelly Bean and now Kit Kat. If you're not up for the lengthy read but do have a passing interest in learning more about Android I suggest just skipping to the Ice Cream Sandwich section and reading from there.
Just looking at the main pic that leads into the article I can't help but inwardly groan when I see Gingerbread on the bottom left there. Oh god. My first Android device was the Nexus S 4G and out of the box it came with Gingerbread, which was kind of a big deal then. I still remember how excited I was when I got my phone, I think I lasted all of 30 minutes before rooting it. I was a young Android aficionado even early on in the OS's life.