I formatted an external HDD using mk2fs.hfsplus with HFS+ on my Linux box (FC10, Kernel 2.6.27-21, hfsplus-tools-332.14-7.) The previous FS was FAT32.
Everything seemed fine. The drive mounted, I could R/W. I filled it with media and returned it to the Mac owner.
When the Mac owner attempted to mount the drive, OS X came back with the message "Verify volume failed. Unrecognisable...
2009-04-23 21:18:06 UTC in Linux HFS+ Support