I ride a 6" bike (Ventana Terremoto) for XC/AM/enduro (or whatever it's called this week) and after 2 years on this type of bike I reckon that it is probably overkill for most of the riding I do..
Just because it is possible to make an 8" bike that pedals well and doesn't weigh too much doesn't mean that we actually need that much travel.. More travel is a good thing to a point - the trade off with longer travel bikes (higher centre of gravity, high BB, slower handling etc) may mean that we get bikes that are for suitable for 5% of our riding instead of the 95% of our riding. So we put up with compromises for the majority of the ride to make a small proportion of our riding a little more fun.
I was talking to a riding friend the other day who about the bikes we ride (Foes FXR, Intense 6.6, Ventana Terremoto) and we agreed that these 6" plus "trail" bikes are great fun, but they are really only good fun because we can't afford to buy a 5" light XC/trail bike and 7-8" light(ish) freeride/DH bike. We suffer on the climbs because these bikes make the downhills heaps of fun. If Australia had an abundance of trails that required more than 5-6" of travel, I'd give you a very different answer, but we have pretty much pure XC or pure DH type trails, with not many that hover between the two (a couple of You Yangs trails like Trav's track fit this criteria).
I wouldn't buy a bike like the Canfield unless I already had a 5-6" trail bike and wanted the Canfield as a light freeride/DH machine that was for very specific rides. I love the idea of this bike and the reviews sound good, but I think Australia has a pretty small market for these bikes, unfortunately. Then again, I'm fat and old so may not be the right person to ask.