Dragonhunter and tempest seem underwhelming, the dragonhunter was just a very poorly received elite in general and tempests problem is the absolute insane strength of the elementalist in EVERY single game mode. It is hard to get excited when your class is pretty much OP already.
Reaper is flashy and kinda fun, but just not very good. As always a really strong class, probably the absolute best at it right now. Haven't played mesmer at all, but most people I've talked to seem to agree that it is overpowered at the moment.
The zone you could play in was very restricted so it's hard to judge the quality of the overworld maps. Enemy design is somewhat interesting, the whole growth/plant thing gives them some freedom to introduce more freakish looking designs, there's also dinosaurs and that is always cool. Some enemies shout and curse at you.
In terms of combat, some enemies are absolutely deadly if you're solo, most events on the other hand though seems still as zergy as ever. Then again, we haven't really seen the "big" enemies of the expansion, no Tequatl style fight yet and we still don't know what the challenging group content is supposed to be.