It's definitely the most complicated healing spec of the 6. Not only is it naturally complicated with a lot of very situational options (meaning you can't just pick one way to heal and do that all the time, it just won't work), but being a new class causes major shifts every patch. Not only do you have to know how to play the spec, but you'll have to be so familiar with its inner workings that you can quickly adapt to the numerous changes that happen month to month. If you're already good at healing in general you should be fine, but if all you know is how to play your class... you might have problems.
As for fistweaving, yes you always want to be in melee range if you can without getting killed. To that end, Mistweavers are technically classed as melee for fight mechanics, so you can stand anywhere that a Rogue or a Warrior could stand and not wipe the raid. We don't use balls-out fistweaving very often, but simply using Jab to generate Chi is used on almost every fight. It definitely gives it a very different feel than other healers.
I reroll 3 weeks ago from Hunter to Monk MW. And I was so excited by monk. He has so many play styles, You can chose time to fist weaving or range healing. Really super class. But After BIG nerf 25 man Monk healing is so low... I am recommending you to pick up disc priest now