i just got an SLS. i've driven the 599 and i think the MB is the better and more fun car IMO. you should try it.
I test drove the MB SLS today. Car is a real hot rod. Comfortable although I'm 6'4". I am tempted to give it a try. Quite a few are out there with low miles, discounted off MSRP. Big question is how many will they build. Will the car depreciate like a stone? If in limited numbers, it may retain some value? I guess I'm spoiled since my reference point is the GT which has done pretty good for a car now 6 years out of production.
I did go look at a 599, but the one I was interested sold so all I could do was sit in it at the F dealer. There are tons of 599's for sale currently. Ferrari is about to unveil the new successor to the 599 and that will probably drive prices of 599's down further. They are going to follow the deprecation curve of the 550 and 575 IMHO. Speaking of depreciation, I was offered a pittance for trade in on my Stradale. 14K miles, pristine, serviced, never tracked. Lesson learned on modern mass produced Ferrari's. I think I'll sell it myself!
The other car I like is a Porsche Turbo S. Haven't been able to test drive one yet. A few 2011's out there. AWD, PDK etc.