I could be wrong but I think the buzz around the Giant Anthem frames breaking has been confined to the alloy 29ers. It's not an issue that cme to my attention with the 26ers. No, I wouldn't buy a used one either.
Simon, I think you're still over my way somewhere? I've bought most of my bikes secondhand and have had good experiences, but you do need to know what to look for. If you'd like a second set of eyes, I'm happy to tag along on a Saturday arvo if you're driving.
You can get a *very* good used bike for $1500. To get something decent new you'd be looking at a minimum of $2.5k.
A used option that might be of interest:
Medium Cannondale Rize:
http://nobmob.com/node/46176 I have the alloy version and it's a real nice bike to ride
The same guy may have a 2012 Scalpel for sale (also a medium) for an excellent price. Might be a little bit more than your budget as it was/is an $8k bike new, but it can't hurt to ask. The Scalpel 29ers have a reputation for being tough bikes. I have a mate who breaks bikes regularly, and destroys forks and pivot bearings (no way I'll lend him any of mine), and it's survived two years under him with no structural problems.
If you want to throw links to any you are looking at my way I'm happy to let you know what I think.