Treantmonk and two other YouTube folks just rain a public playtest that included him with a 15th level monk. It's just one playtest, just three scenarios, three different maps and groups of foes, and one short rest. So it's an extremely small sample size. But all that said, the new playtest monk functioned very well. It didn't seem overpowered, but it was very effective. It did not outshine the spellcasters nor did it play as lesser to the spellcasters. It was very complimentary to the spellcasters and they were very complimentary to the monk. A lot of the effectiveness of the monk was not in DPR but in other things, though its DPR seemed fine.
Weakness: It was highly vulnerable to Telekinisis, which does not give a save but rather an ability check. Possible that spell will change in the new rules, but it took someone else breaking concentration on the caster to "unfreeze" the monk.
Strengths: flight (Elementals monk 11th level ability Stride of the Elements), speed (I think 110' with Step of the Wind dashing as a bonus action, base 30' + 25' from monk level 15), grappling, ability to carry someone else along (10th level Heightened Discipline feature - so he could fly an ally 110' essentially for free), ability to deflect some damage and reflect it back on the attacker, number of attacks, and stunning. He also did a bit with the 15' reach (3rd level Elemental Monk ability) and energy attacks with pushing and pulling (3rd level Elemental Monk Elemental Strikes ability).
But really, a whole lot of it was grappling and flying a disgusting amount, so able to do things like grab foes, fly them up, punch them a lot, and drop them into a spellcasters field of damage like Spirit Guardians or the new Conjure Animals swarm, sending them prone, taking falling damage, spell damage, etc..
