[arch-general] Building packages from AUR/ABS

Hi, I've built Firefox 21 using Firefox 20 PKGBUILD, changing versions and reading the README notes on the source tarball, just for try. Should i expect any issue when installing? Is this a good method for a general purpose upgrading / downgrading? I mean, I can wait for this package because is in the extra repo, and is widely use and i know is going to be updated ASAP, but it should be good to know for other packages from AUR, or the main repos that doesn't get updated or get unmaintained. PD: I always flag packages that i found out of date! :)