My laptop makes it from cold start to gdm login screen in 9~10 sec, running bog standard Ubuntu 12.04, by virtue of replacing the system disc w/ an SSD.
Add another 3-4 sec for initial login. Yes, even bloated desktop login is acceptable w/ faster disc IO.
Not that I find boot time that interesting anymore: sleep/resume has been solved, I almost never actually shut down anymore.
My biggest issue is NetworkManager taking its time to decide where I am and getting the appropriate WiFi up.