Is HotU generally considered easy? I imported my lvl 13 cleric from SoU and have played to level 2 of the dungeon. So far there has been little challenge. Do things get harder in the future? No plot spoilers please. :)

Clerics are generally considered to be a pretty powerful class to begin with, but that aside, HotU isn't terribly difficult, but there are a few battles that should provide a challenge later on. What difficulty setting are playing the game on, btw? You could consider turning it up if it's just too easy.

D&D hardcore rules. I'm not really the powergaming type but the cleric seems pretty powerful yes. Especially since the buffs can be made last long and usually you can find a place to rest if you need to.

Yeah, that's likely part of the issue (playing a Cleric). HotU isn't terribly difficult though, especially since you can pick up some damned powerful gear to kit out your character. But it's still well worth completing, as the story is quite good.

Don't recall it being particularly difficult.
But that has a lot to do with what kind of character you have and whether you've build it bass ackwards. Even much more to do with players usually doing the stupid mistakes in OC or SoU and generally knowing how to play NWN by the time they're at HotU.

I think I played it in easy anyway... :)

The fights should be easy if you are prepared, but never underestimate some of the later battles.