How does it compare with the CLR, or things like LLVM?
The biggest problem I've had with the CLR is threads bouncing between CPUs but I'd attribute that to Windows as I worked around it with some Win32 calls to pin threads to processors.
Can't really compare to LLVM, I haven't personally encountered any of the known llvm bugs (clang to be fair) with Obj-C.
I'd try to increase the revenue my server generates rather than decrease the cost of servers, but I'm the kind of guy who thinks it's possible to pull more than 5 cents an hour in revenue from a server, but if you only get 5 cents per hour then it would be important to use linux so you maintain your 2 cent per hour profit margin.