You have no idea. When I was in the Apple store waiting to pick up my laptop, I heard a nerdy looking boy with pimples telling an older couple that the only computers that Apple sells that can run Photoshop are the Mac Pro's, and that a Mac Mini isn't powerful enough for simple color correction.
They were upgrading from a G3 iMac for crying out loud!
I hear you... when I was picking up my new 24" LED to go with my MBA Rev B with the display port I overheard a customer asking one of he Apple sales rep (reminded me of the bloke from the I am a Mac ads, cocky and thought he knew his stuff) if he could use the new 24" LED on his Mac Pro, they guy said "of course you can, you just need an adapter" The customer was about to buy one when i jumped in (did not want the guy to lug it all the way home just to return it) and explained that it only works with a mini Display port. The sales rep politely explained that i was wrong, so i asked him which adapter he should use, after a short walk to the adapter section the Apple rep, the rep handed the customer the Mini Display port to DVI adapter.... at this point i asked him how you connect two female mini display ports together...at this point the cogs started to turn...and after further consultation with a genius who had to talk to his manager, they realized that the 24" only works on a computer that has a mini display port.
I recommend to anyone that has an issue with their mac, do your research (these forums will probably have the cause/reason for it) and then see a genius, its a title and not a reflection of their actual ability.