Everyone needs to stop their moaning & complaining.
First off, for people coming from an iMac 3+ years old, this will be a huge improvement. It's not like most people upgrade their $2000 computer every year.
Secondly, every component (especially the 680MX) used in the new iMac line are fairly substantial upgrades. I saw people from PC/Laptop gaming forums drooling over the 680MX, something probably only the iMac will get. What else was Apple suppose to use? An Nvidia 7 series or Haswell? Oh wait, they're not out yet!
Lastly, I'm tired of hearing about the loss of the optical drive and how bad the new design is because it's "too thin." The absence of the optical drive was a long time coming, don't act surprised because it got removed. If you're still the person burning DVD's of your family vacation for your parents, then know you're one of the few and there are still options to accommodate those needs. Now, if you're a professional, you're probably authoring to Blu-Ray anyways. Loosing the optical drive shouldn't be a big deal because you probably own a Blu-Ray external burner already.
Yes it is THINNER! We can all see that. I am confident that Apple Engineers who make 200,000K+ a year figured out a proper way to cool these or they probably wouldn't have released them.
To me, you sound just like a bunch of babies. By all means though, stick with your iMacs with optical drives. It'll just help those of us who want one, get one quicker.