I can get a TiBook 500 for about 1200 euros. What's the current value of
such a powerbook?

The PB has 768MB of RAM, and all the other standard configuration.

Now, with that configuration, what can I expect from X in terms of speed
and efficiency? I'd like to use it for every-day stuff such as
web-browsing, mail, programming, and an occasional dvd view.