I wanted to add if your on the fence 21 or 27. There are alot of studies to say more screen space = more productivity. And whatever you do in life productivity is a good thing.
Plus if you plan to watch movies on your imac it has to be 27.
I also read somewhere if you unsure what to buy in terms of specs buy the middle spec machine. The mid machine doesn't have the bells and whistles you'll never use on the expensive machine and will be nicer to use than the low baller machine. So is the best value and will be resaleable if you plan to upgrade after 2 years of 3 years applecare.
Soo...
Buy the low end 27 machine best bet if your thinking 21 or 27!!
Thanks that helped quite abit. Yeah I'm now thinking gettin the low end 27inch but I guess we will have to wait and see if the same screen sizes will be used.