Johnson has bowled for entire matches in the 135-145 range this summer. He's more like 135-155, which just goes to show how unpredictable he is (and not necessarily in a good way). Mentally I've started to classify him as more of a LFM most of the time.
Hmm that's a little harsh. He's a 140+ bowler. If he's in the 130s he's warming up or bowling cutters. But at the same time he's not a 150+ bowler either. 140-150 is a fair range I'd say. Proof? Cricinfo has Hawkeye for some games now and Mitch was measured in the 2nd and 4th ODIs v West Indies.
In 2nd ODI his average was 87.4 (140.7), highest 90.8 (146.2)
in 4th ODI his average was 87.4 (140.7), highest 93 (149.7)
Considering slower balls bring his average down, he's definitely a 140s bowler.
I think you've described Peter Siddle pretty well though. Sometimes he can crank it up to 150 when he's really in rhythm. But most of the time he's high 130s, maybe low 140s.