I've had my 8300 for a month now, and used an 8100 for two years prior, and Epson 9600 and 9800 prints before that.
I think the Canon x300 printers are an exceptional bargain. Let me say at the start that I believe image quality of the comparable Epson and Canon printers is top notch with only minor gamut differences. It's an odd time to be buying a printer because raw image quality is almost last on the list of features to compare. Operationally, I think the Canon beats the Epson in just about every way; they're fast, virtually no head clogging issues, even less ink wastage in the x300 series than the x100 printers, no ink waste at all when switching from matte black to photo black. Both printers hand rolls and sheets easily, although the straight-through paper path of the Epson and higher head height makes running metal substrates possible.
One big difference in Canon's favor is the print plug-in module that is accessed from Photoshop's Export menu. It's dead simple to use and has no issues with any version of the Mac OS (I'm using OS X 10.6.3.) Currently, it won't work with Photoshop CS5 in 64 bit mode (you have to run PS in 32 bit mode) but Canon says the re-write of the plug-in is in the works.
I run my printers in a commercial, fine art environment and couldn't be happier. The x300 line does have improved gamut and noticeably better scratch resistance. Even the x100 ink was less prone to flaking than Ultrachrome ink.
My experience backs up what I read in Scott Martin's review. I think you won't regret it if you go for the 6300.
Rob