Those who do not like seeing high their CPU usage stats when doing things like networking, should consider buying a Mac Intel. However I think this is due to the tremendous raw power of these machines than to changes in how MacOS X deals with networking.
I've always said that to me it is OK if CPU monitoring tools tell that the CPU is doing heavy work even if the system is only downloading something from the net. In fact although CPU values are high, the system is fast as ever, so I wasn't concerned.
Well, on MacIntel you don't even see high CPU usage stats.