How does that compare performance wise with a 2Ghz M-P4?
I have no idea.
Are you going to try Linux on it?
No. OSX has pretty much everything Linux does and then some. Most open source compiles cleanly for OSX and its getting good support as a peer unix. Plus its pretty much install and go with (mostly) sensible admin tools.
I'd like to play with OS-X one of these days...
You really should. Cocoa will rock your world. Get a cheapie like an iBook. You'll love it.