I noticed that on my recently purchased (late May) 18 month old S205 C250 AMG line BlueTEC, the aircon didn't seem to blow as cold as my old 2010 C250 CGI.
After about 3 weeks, I booked it into the MB dealership where I purchased it, for them to check it out (whilst I waited). After around 2 hours, they said they could find nothing wrong and "the newer models do not get as cold as the older ones"!!
In fairness, in the 2 week wait after booking it in, it did seem to be getting colder, which I put down to possibly the aircon getting more used, following several months sitting round the MB dealership's network? (I had checked the "is my car taxed" DVLA website prior to purchase and last time it had tax was end of Nov 2015).
It seems to be okay, though to be honest, we've not had that much hot weatherr to test it fully, here in East Kent.
I would have been more reassured though, if the dealership had produced some sort of test results showing the temp of the cool air coming out of the vents (like many local mobile A/C outfits have done for years? Too much to expect from the "experts" at a lot of MB main dealers, I suspect these days?
Phil