Release Canidate number 3 (assuming that there isnt going to be a fully "stable" version) wont be a finalized version of the software. So it would be best to install now, wait for the next releaase so that you can figure out how its works on your server. If there is a problem, you can discuss it with people on here and figure out if its with the software or with your server configurations. Saving you headaches down the road. Also, there are only a small handful of people with actual installation problems, the rest is just misconfigurations with many problems resolved with each update. I've installed this software on three servers in total (one main, one test sever that I've changed severs twice) and have yet to had a problem that wasn't of my own stupidity.
Risking sounding like a parrot, I'd also like to add that every XF update I have gone through so far has been a wonderfully smooth experience, rather than the "sacrifice a few virgins and then hit upgrade-and-pray" process I got used to being needed for vB upgrades.
I purchased XenForo, am ftp'ing it to my server now. An excellent product + the best online community I've ever seen sold me. Honestly the last part had every bit as much to do with my decision as the first part
I predict a Thursday release. Friday support and bug fixes . Note: Not saying gold is coming. Just they release it and people report a lot of bugs within 24 hours of release so they fix and give support.