I'll admit the endless compiling was often torturous, but I have the Gentoo docs to thank for most of what I know about the innards of Linux and operating systems. Bet I'm not alone in judging the time spent worth it :)
My time in Gentoo was absolutely worth it for the same reasons. There are dozens of us! Dozens!
I still recommend it to people who are serious about diving into Linux.
I'd say I learned more by playing around with Slackware, but Gentoo provides all those nice tools to mantain a consistent system.
Actually considering it for the next build. 16 amd core CPU. Probably 4 machines to crunch on something in the next few years.