Isn't that a bit on the hot side? I'll usually hover in the mid/high 40's during normal use. I've noticed Lion runs a bit warmer than SL but in the 70's seems too hot?
70s definitely seems hot. My MacBook Air 11" from last year has been running hot on DP4 and the battery life is horrid right now. The processes "mdworker", "storeagent" and "mds" have been hogging my CPU causing my temps to get high and my battery life to drop horribly.
I try to keep my CPU temps in the 50s Celsius, and in order to do so, my fans have pretty much consistently been running at 4500 RPM.