I found the earlier units (up until the 2.2/2.4BTC pricing rounds) usually ran in the 48-54 degree range when i clocked at 387 or 400. The newer revision tends to be happier sitting in the 43-47 degree range, perhaps due to the slightly bigger fan.
I'm seeing the same, the units from the 1.45btc batch are running 7-8 degrees cooler that my older ones.