I'm finding the same. On a P3-1Ghz (Mandrake 9.2), everything compiled (yes, WxGTK too). On my system it uses a minimum 20% CPU usage although I have got it doing a fair bit of work. It needs a way to tune down its updating of transfer views etc...
Don't get me wrong here, aMule is a kick ass program, does the job really well, just uses _way_ more CPU than the last aMule I had (1.1.2). Oh yeh, that Gnome status thing rarely works too but thats just superficial.
Michael