I like the Seikonic 558-L (I think that's the model ... the one with the built-in PocketWizard transmitter).
A couple of reasons why I use a light meter outside of the camera:
1) To get a true reading on the actual light hitting the subject. Since I'm often shooting a bride in a white dress and a groom in a dark tux, I can't get an accurate in-camera light reading off of either one of them because they each reflect a different amount of light. Expose for the white dress and the tux disappears into darkness. Expose for the tux and the white dress is blown out. So using a light meter, I hold it up to the couple and get a reading off of the light hitting them and use that to set my exposure.
You can, of course, use your histogram and adjust exposures to avoid the blinkies... so while the light meter saves time, it's not absolutely necessary.
2) On the other hand, when using strobes... there is no way to measure the amount of light coming from a strobe using your in-camera meter. And so you'll either endlessly play with the histogram and the varying the power on each of the strobes. Or... use a light meter and set it up quickly and correctly the first time.
3) The light meter I have has a built-in spot meter as well... so if my subject is distant, I can look thru the spot meter and get a reading on the highlights and the shadows and quickly come up with an exposure that will try to keep both of them in range.
Have fun with that Mark II. I'm jealous! 