+1 on the Mike Focke reference. It's been around for awhile and I don't know if it gets updated, but it's got a lot of good info with no real expiration date. (Probably the sticky reference is good too, though I didn't discover it until after I got my Box, so I haven't much read it!)
Unless you're a beast on them, I've never found myself going through brakes all that quickly...not at all. If you plan on hitting the track I'm sure that can change very quickly. One thing that some people do go through quickly is tires, especially (
duh) rear tires. Though tires don't last me quite as long with this car as with others I've owned, I really can't say I have had that problem either. I accelerate hard at times but am not doing burnouts; I'll even have the rears gently break loose at times when accelerating into a turn---keeps the reflexes sharp

. At this point, I've got over 25K on the tires. Admittedly, the rears are
really in need of replacement, but I've heard about people needing to do that with rears after not much over 10K.
I had some issues over the years---CV boots, one coil pack, one wheel bearing, water pump, alternator. Most of the work I've done myself, and I'm no mechanic. If you're interested in wrenching yourself, I'd recommend the
Bentley Service manual and the
101 Projects for Your Porsche Boxster book. The former has a ton of detail and, and if you look around, you can probably get one in the neighborhood of around $50. The latter is inexpensive, has nice pics, and is a helpful addition, though it has occasional inaccuracies. There's also a DIY site by a really good guy named Pedro. It's very useful if you want to undertake any of the projects that happen to be discussed there. Check it out at:
DIY Projects: Do-it-Yourself Repair and Maintenance for your Porsche
I haven't made my mind up on the IMSB. I'll probably need a clutch before too many more miles, so logically I should do it then. Probably will. But I'm quickly getting to the point where, even if the IMSB grenaded I'd feel happy to have gotten this car. It's been that much fun.