The Macbook Pro is sort of ok, but it is still a TN display. You can do color sensitive work using it, but it does involve guesswork. If color accuracy is crucial, don't get an Apple laptop. In fact, don't get a laptop.
Oh certainly! Stand-alone monitors are not necessarily better than laptop displays. The display in my Macbook Pro is head and shoulders better than my piece-of-shit Samsung 24" (245b) TN panel. But Apple or Eizo or what have you stand-alone displays are significantly better than both. They usually cost more than a whole computer, though... I don't know about the current iMac, but the older 24" ones were actually a pretty good deal — monitors of that quality will set you back a fair bit of money. It's not just any 24" panel in them.qft.
no laptop is going to have a screen accurate enough for precision color work. hell, 90% of standalone monitors aren't up to the job lol