I've heard it go as far as 70C-90C idle
No that's just ridiculously high and at that point you definitely have a problem. My 2400+ XP Idled at 64C with stock heatsink and fan, with no other case fans and one side open, max temp was god knows what in the 70's I never payed attention at the time because I didn't know...however these REALLY aren't good temperatures...
Good temperatures should be in the Mid 50's and low 60's on full load if you don't have good cooling, but from what he described he should have better than 60C unless it's just hot in the room. I keep my overclocked CPU in the 30's celsius and it goes up into the 40's when I game... I definitely would suggest getting better cooling, but yes AMD's do run a little hot and can get up there pretty high but as far as 70C-90C idle this is simply not true, it'd be way on the verge of frying and instability at that point.