hey, exactly the same machine as you
with:
ram at 2gb
hd at 7200rpm
i totally agree with the poster above about not wanting to do anything other than light video editing on this machine, its not bad and it will just about get you through the next 2 years, but i would highly suggest getting a macbook if you possibly possibly can. saying that, i've maxed everything out and overclocked the gpu a little, and if i really had no other choice it might take me through the next 2 years, its just compared to even the previous gen macbooks there really is no contest. This powerbook's geekbench score is around 600 (670max), whereas macbooks were around 2000 on their 1st generation, now theyre around 2500/2600. it is an absolutely massive difference.
in answer to your garageband requests, currently i have the latest webkit build(think safari) with 5 tabs, mail, itunes and a pdf open.
garageband took 31 secs to launch.
when using it its fine, i've never have many issues, but the beachball will become your friend, also spaces and elements of the gui hang at time while its crunching.
there is one other thing i will say, youtube destroys this computer, adobe really need to sort out their flash player.
shout if you want to know anything else
b