Same with my late 2007 MacBook. Idle temp just hit 40°c and fluctuates between 40°c and 43°c. Prior to installing the 10.7.1 update I had never seen it lower than 48°c in Lion. Unfortunately I don't have temps under Snow Leopard to compare with.
For greater details the fan is not simply running faster at idle it still stays at the minimum 1800rpm. It does increase as the temps increase of course but as far as I can tell it seems to increase fan speed at the same temperature/load trigger points as before, and certainly not sooner.
Even at full load things are improved, I'm in a good position to test this as I have been pushing it recently while deciding if changing the thermal paste might be useful.
When running CPUTest 0.2 to stress things temp would reach 94°c and stay there. Now it's spiked at 92°c but instead of staying there it actually goes down! to 87/88°c and spikes up again every now and then just for a few seconds though.
Don't have measure for ambient room temp but it must be similar, if not actually 1-2°c warmer today.
Not sure whats changed but being one who prefers quieter use I like it as it takes longer for fan to get to full rpms
Sorry for long post about MacBook in Mac Mini thread but I thought it seemed relevant given the Lion update and I do have a Mini point to follow...
I'd be very interested to hear if other new 2011 Mini users were experiencing the same, and if indeed the Fan was not spinning faster to help with these results as I'm considering purchasing one but some of the early reports of fan hitting 5000+ rpm seemingly all to often and easily were pretty off putting.
