Day 1: Ooh, pretty.
2-3 days: I fucking hate iTunes. Luckily ports install mpd works.
1 month: Ooh, the pretty magsafe connector saved me from dropping it when I tripped over the wire.
1.5 months: Arrgh, finally numpy works.
2 months: I miss XMonad.
3 months: Fuck, random C/C++ library (e.g., amqp_lib, boost for a while, quantlib, some Fortran medical imaging libraries) doesn't work. Or maybe it would work if I messed around with it more. Neither do many Haskell libraries (e.g. HFuse). I never managed to get postgres working either, though I've heard others have.
4 months: I want to get work done. Open up virtualbox, boot ubuntu server in a VM.
2 years later: load linux onto a thinkpad. Woohoo!
[edit: I am being a little unfair to the macbook. It has one fantastic feature which I still miss: keynote + LaTeXit + that little remote control. This makes pretty and very effective scientific presentations. OpenOffice Impress is not in the same league. It's less relevant to me now, since I'm no longer an academic mathematician.
Also, I don't mean to be unduly negative on macs. They just didn't satisfy me as a development box.
Lastly, things might have changed recently. I gave away my macbook early this year.]