Here's the fun: auditing it.
More fun: once this code goes live, livejournal will run a lot nicer and all your friends will be happy and offer you sexual favors for helping audit it.
Here's the prize: find a bug (either "this doesn't work" or "here's a security hole" or "here's a patch") and I'll give you or a friend a year paid account.
A ton of shit got changed... the likelihood of you finding a bug is quite high. Hell, jakd found one yesterday and I wasn't even soliciting bug reports yet.
 It's actually the revjim "patch of pain" to make everything $dbarg aware that'll make the site fast[1.1], not my changes, but my changes started to clobber a lot of revjim's work, so we held back updating livejournal until everything settled for awhile.
Update: files calling LJ::do_request are the ones prone to failure... go test these:
bradfitz@goathack:~$ grep -rc "LJ::do_request" htdocs/ | grep -v :0$