Welcome! How did you tri-boot, if I might ask? Did you just make 3 partitions and install an OS on each one?
Yep. I use reFIT as the boot manager. From a fresh OS X 10.8 install, I split the hard drive into three partitions, installed Windows 8, then installed Ubuntu. The main caution was to make sure that Ubuntu installed GRUB to its own partition instead of attempting the MBR.