It'd have to be a CD-RW, and it'd be a bit cumbersome to lug a laptop around with you every full moon (never mind the transport issues - there are few places to perch a laptop on a broomstick). Also you'd look a bit out of place at the coven. (Which is slightly ironic, really - most people get odd looks for using books when everyone else is on their respective computers.)
Not really - you could just type your notes out when you got home; no need to actually take a laptop with you.
And you wouldn't necesarrily look out of place at the coven - aside from the fact that there are online covens, there are probably also those who take their computers to meetings.
As for transport issues on a broomstick - saddlebags.