Seriously, why the Linux hate? Yes, I'll third that the Octane's hardware works much better under IRIX and that any of the really unique stuff like video capture and accessories probably don't. However, the original question was has anyone gotten Linux to work on their Octane. The answer is yes, I have. Kumba (the Gentoo-MIPS lead) and Frapazoid are two other forum members who I know have as well.
The Octane isn't quite as crippled under Linux as some posters have suggested. Impact based cards have some degree of X acceleration. The VPro cards don't, however. The audio works, onboard SCSI works, the Octane tape drive works, and PCI shoehorns and card cadges work (and support a large amount of hardware IRIX doesn't like USB cards). I'm not 100% sure on the status of the XIO peripherals, some cards work (anything that internally uses a PCI bridge) including SCSI, Gigabit, and Fibre Channel. The only other thing I remember testing was the SCSI floppy, which didn't work. (Actually caused constant printks so I had to pull it).
Somewhat unfortunately, all of the support is currently only in Gentoo. I highly suggest the Gentoo SGI Live CD. If you have a SCSI CD-ROM, just burn it and boot. If you like what you see, you can go from there. http://dev.gentoo.org/~kumba/mips/livecd/x-rc6/
Actually read the readme since its not a normal ISO image.
Getting the kernel patches into Linux-MIPS and mainline is a goal of one of the developers on the mailing list who recently added a lot of SGI support (audio drivers for O2, Indy, and Indigo 2, among other things). Also, I'd like to point out that 2.6.27/28 will likely make the VPro issue moot as Linux will get kernel mode setting. That means Radeon X1550s (or whatever's the best PC PCI video card with Linux drivers around) for our SGIs. I'm fairly sure an X1550 is better than a V12 for the vast majority of video tasks.
Anyway... the point is that Linux support for SGIs is being worked on and will get better as time goes on.