Interestingly enough, you should not attempt to install new operating systems on machines that have faulty logic boards. I began to realize this after my Leopard install failed about five or six times.
As a bit of backstory: a few months ago my MyBook died (theoretically), which led me on a crazy chase to figure out what the heck was going on with my Macs and hard drives. The second and third hard drive replacements worked over USB but not Firewire. Long story short, it seems that some cheap Western Digital Firewire cables fried the Firewire on my iMac, my MacBook, and the drive itself. Three replacement hard drives later I found this out, and promptly got my MacBook's logic board replaced to fix the Firewire ports. My iMac is currently in the shop getting the same treatment.
Unfortunately, it seems I got a faulty logic board for my MacBook as a replacement. Firewire ports work now, but two or three times a day it just powers down... no errors, no logs, nadda.
Naturally, an OS update would be prime time for those shutdowns to occur. So that happened a good five or six times until the one happily went through without a hitch, which brings me to the present: typing on a new Leopard install.
It feels good, too.
My friend recently got his MacBook zapped by a glass of water. It looks to be a fairly total loss- must have been a short inside of it somewhere (the MagSafe connector doesn't light up when plugged in, and the battery doesn't light up either).
Luckily, I was able to help out some tonight, and it ended up being pretty painless. He brought over his hard drive and I swapped mine out for his. Fortunately for him, the hard drive seemed unaffected, and we were able to make a full backup of it. This is the point where I really enjoy OS X. He didn't have an external hard drive to back up on, so we just plugged in his iPod, reformatted it, and then clicked "restore" within Disk Utility. That way you can basically make mirror the hard drive to another. It worked great, and he should have a clean backup of all of his data for the next time he needs it.
I know through this process you can make a bootable drive, too, although I don't think his iPod was made bootable in our case. But that would be another great way to do it- mirror your hard drive to an external drive and then you can boot right off of that drive like nothing happened. From that point you can use Apple's migration software to pull all of your settings onto a new Mac, or you can just copy that drive again to a different Mac and you're back to where you're started. Nifty stuff.