I have 9.1-PRERELASE and I've had it since before Thursday:
hiryu@hostname:~$ uname -a
FreeBSD hostname 9.1-PRERELEASE FreeBSD 9.1-PRERELEASE #0: Sat Aug 18 17:16:25 PDT 2012 root@hostname:/usr/obj/usr/src/sys/HOSTNAME amd64
9:57AM up 7 days, 15:54, 3 users, load averages: 0.02, 0.03, 0.00
Sun Aug 26 09:59:54 PDT 2012
I also verified I have the latest source for 9.1 today. Why is it 9.1-PRERELEASE instead of RC1? I don't know... But maybe the cvsup mirror I'm using is lagging behind? But that would be a few days behind. Maybe I'll ask on IRC.
Note: I run FreeBSD on my home server (as you see here, and since it's not so mission critical, I can upgrade it to a PRELEASE without real cause for concern) and my server at the colo (which is still 8.3, I'm waiting for 9.1 before going to the 9.x series there). Otherwise I run Kubuntu as the desktop OS on my desktop, my laptop, and the family computer.