You do know that you can't use PowerBooks for your exams, etc.. at least not at any schools I know of. PC only. And the PC mimic software on a mac won't cut it. You can of course use the PowerBook for note taking, etc. though.
I have a huge collection of accessories for my PowerBook, because I'm a geek and the computer is just so damn cute I have to buy presents for it.
People at my school rent PC's for exams. The reason why they require PC's is because you have to use ExamSoft, a program that locks you out of your desktop while you are writing your exam. ExamSoft is for PC only. We are protesting the use of the software because we already have an honor code and that ought to be enough. We'll see what happens, but there are school that have been successful with this battle, so we are hoping to follow in their footsteps.
The last people I would trust not to cheat are a bunch of panicked 1L's taking their first set of exams.
There's simply too much motivation and temptation to gain any edge possible, and it would be far too easy and efficient to cheat if you had access to your desktop.
Not to mention that law students are generally pretty shady ethically anyway. Once you know how laws are made (the old sausage analogy), it's hard to treat it with the same respect.