its safe to buy 27" imacs anywhere. always has been.
it comes with a warranty in case something is wrong with it.
I know of a few people who are waiting to purchase an iMac when the refresh comes out. Right now, there seems to be too many problems with this current generation. If you can, just wait it out. Even the current refurbished models have yellow tint in them.
My 24" iMac has a $1630 repair bill on it, so it's pretty much a necessity at this point.
Ooooh that hurts...What the hell is wrong with it?
LCD has gray lines through it, superdrive spits out disks, bluetooth disconnects randomly. It's only ~18 months old but I do work computers quite a bit.
The point is to avoid having to deal with taking it in to get replaced or repaired.