Seems to be a good number on a single CPU 1.3 with the account types we are using. The key seems to be to keep an eye on the usage to see that no poorly written scripts are running and hogging up the server. Ours stay way under capacity and work great! All Dell servers 1U 1550s
How would you know what script or what user that is causing the high load? When you look at 'top', it only shows HTTP as nobody or MySQL as mysql, etc..