Processors have rarely been the performance bottleneck on any machine (PC or Mac). So, waiting on a slight higher processor clock rate is rarely worth the delay. It's usually the hard drive and motherboard slowing everything down. Especially on iMacs where you basically have a desktop monitor, desktop hard drive, and pretty much everything else in the machine is a laptop component.
Me, I usually wait. But then, I'm one of those douche bags that just likes the bragging rights of having the latest thing (no matter how short-lived). 🙂
I've been waiting so long for an upgrade and can't wait to brag for a minute..😀 I'm not so concern with the upgrade in the iMac being the speed but I'm hoping the rumor about the improvement in screen is true. I was told the screen after prolong use can be bothersome..(glare) I will wait it out and see..if all else fails and I don't feel the upgrade is worth it, I will just buy the current refur model and save a few $.