I have the MacBook Air with 24" ACD and recently bought the 24" iMac. Then I attached the ACD to the iMac so I'd have dual 24" monitors and the my MB Air wouldn't be tethered to anything. What prompted me to buy the iMac was I found I was leaving the Air on my desk hooked up the the ACD and using it as a desktop too much, I'd be too lazy to connect and disconnect the cables/usb hub etc ... That left me thinking that's not really what the Air was designed for, it's not meant to be tied down it should be left free to float around as the beautiful machine it is yes, I love my MBA. I've been real happy with the iMac dual monitor set up, it's hard not to be, but too use that plus the MB Air plus I also have an HP Tower for a HTPC that also serves for back up, server etc, all is working well. Except, being the mac addict I am I can't stop about thinking about the 15" MPB. To buy it an add it to my existing system is 'nuts'. Not that I don't want to but I know I shouldn't. As good timing may have it coincidentally my wife is wanting to upgrade her computer, I with good intentions suggested she buy the 15" MBP, she's 90% at the desk but 10% away and an iMac won't work for that 10% of the time... but instead instead she wants the iMac on her desk and will use an old laptop when she needs to, that's her decsion, she loves my iMac and she must get what she likes to work on .... That leaves me with the idea that I'll give her my new iMac and go get the 15" MBP for myself and use it as a desktop most of the time hooked up to the ACD, and I could take it with me if I wanted/needed more power than the Air has. Then I get all confused and guilty feeling and I think the wisest/smartest idea is to simply give my wife the iMac I have now, and simply just use my MB Air and the ACD as my 'main' computer, that's the more minimalistic sensible, simple approach, and it is easier to work from 'one' main computer as many have mentioned on this forum. So, I'm in the same boat as you essentially, what to add the MB Air .... if anything??