I bought one of the new imacs a few months ago. It was the thought of running Windows on a Mac that attracted me but it did not work out.
I bought 20inch 2,4 and it did not take long to realise the screen was very poor. Scrolling a grey band from top to bottom produced considerable colour variation which was also different from left to right. Scrolling with the mouse wheel produced an unacceptable flickering and when accessing PC Adviser site all the lines were momentarily black. It was only then I did a search on the many mac problems which exist-and they do!
The operating system is different but did not offer any significant advantages to me. I returned the machine on the basis of the poor screen and decided to stick with Windows XP. I had previously tried Vista but XP is a very solid stable performer now and I preferred it.
I am sure there are many satisfied mac owners but my short experience was not good.
There has been a big price reduction in imacs recently so it could well be a new model is coming soon. I believe that the 24inch screen has similar problems. These problems did not exhist on earlier models.