The monk is all about quick attacks and combos. You can chain a few moves together for various effects, like applying a damage over time effect to some of the more hardy enemies after attacking with quick strikes. The biggest downside is they are just as "squishy" as a Wizard, so you have to be very careful when running into large groups, I learned this the hard way.
Personally, my favorite class was always the Necromancer and the Amazon, but since the Witchdoctor gives me a lukewarm feeling, I am waiting out for the final class reveal, which will most likely be very Amazon-esque since we have yet to get a bow/spear throwing type of class. The monk semi-covers the paladin role, so we won't be getting another mostly melee class.