It wouldn't be too slow -- it would be a great introduction to the world of Macintosh, but if you plan on doing anything "heavy" like video editing or the like, I would suggest looking for a more powerful computer.
For home use, like email and web surfing along with a little PhotoShopping, it would be perfect. 768Mb of RAM is plenty to run the latest software and the 800MHz processor, while not a speed demon, is adequate and zippy.
It's the 17" model as well, so that's a bonus. That monitor is quite nice and roomy for whatever you want to do with it. It also has a SuperDrive, meaning you'll be able to burn DVD discs you make with iMovie and your DV video camera.
The downsides to this computer is that not much is upgradable besides the RAM (which is easy to upgrade) and the hard drive (which is a little more involved, but still possible). You're stuck with the processor and the graphics as they are, possibly for the life of the machine.
All in all, I wouldn't spend more than $800 - $1000 on it, but if you can get it for that, I would say go for it.