I'd say about the same as N64 emulation, actually. It should run fine on your Celeron, but again the integrated video is a drawback. If you've got any spare cash, go and pick up a new video card, but if that's not an option, you can probably do alright with the integrated graphics, as long as you get a good plugin.
<P ID="signature">i need a friend, please be my companion
i don't want to be left alone with my sanity</P>