It seems fine here, where it's been in the 20's the last few days. It's a similar setup (with a larger interior) to our old 135i, which worked really well. We have tinted windows, but never noticed it got warm this summer. This wouldn't be something I'd worry about.
If you want to talk about an anemic heater and a/c, go drive a Z3 Coupe or M Coupe, mine was awful in anything over 90 or under 30. If you were sitting still, the climate control was pretty much doing nothing, and moving, it was still pretty weak. In the words of JC (Jeremy Clarkson, not that other guy), 'it's like there's an asthmatic midget under the dash with a straw, blowing cool air'.