When I was trying to use a PPC Powerbook for playing videos (first a 1.0 GHz Titanium, then a 1.5 GHz Aluminum with 1 GB RAM, and finally the same one upgraded to 1.67 GHz and 2 GB RAM via logic board swap), I found that the only OS where I had decent results was Leopard with VLC 1.1.12 or 2.x.x (playing videos under Tiger was terribly difficult for some reason, and when I could play them, they stuttered like mad). That being said, you might try upgrading your PowerBook to a clean install of Leopard and rerunning your tests before you write it off as uselessly slow.

I used my 1.67 GHz PowerBook online for awhile (for testing), and I found it to be adequate for most things, though using it definitely required some patience.

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