See, I haven't found the game challenging at all. I've taken four classes into the teens (all but the guardian fighter), and at no point have I been worried about dying. Just clickaclickaclicka, Q,E,R and occasional blow the 'daily' nuke when it seems amusing. Damage happens because all attacks root you, but healing potions are on such a short cooldown (and plentiful in the extreme) that it isn't an issue.
Its fairly weird, because the combat is much quicker than 4e D&D it is based on (which is good), but it still feels like spam_attack = win. On the other hand, despite the quests being flat kill stuff (and occasionally item-fetch through rapidly respawning mobs, which amounts to the same thing), there is at least some background. The 4e reset of the Forgottten Realms didn't really convey any sense of anything happening, while this partially ruined city actually touches on the disaster, the spellscarred and other stuff that the 4e books campaign books really didn't. It is just a shame that the gameplay devolves into just murdering hordes of enemies, 3-5 at time.
But there are some good lessons about server stability (it died again tonight) and fundamentals of action-based combat that can be learned. At no point should a game encourage players to let trash mobs hammer on them because you just don't care about their existence. At the same time, the boss monsters should be a real threat. My (3rd) dungeon run of the Cloak Tower, involved being the main target for the final boss. Her attacks were so telegraphed (and I drew all the threat because I was overspamming damage on her, and the guardian couldn't really tank, though that didn't actually matter), that out of 12 charge attacks that were aimed at me, I got hit by one of them, at the bare end of the fight (with less than half her last damage box left). The funny thing is, I consider myself a fairly mediocre player for group play, especially in action games, and I was routinely 1st or 2nd in damage dealing (even when out-leveled by rogues). The game shouldn't be this easy for me. But I can play and watch videos at the same time, because the normal content is really that simple.
At its best Neverwinter is a cheap diversion. But the gameplay is really shallow and easy, so don't spend money on it. And be prepared to get bored of it after a week or so, even with the player-made quests.
@Sparhawk - well, for now you're really going to want to avoid neverwinter if you want character creation. Decent selection of races, but there is effectively one build for each of the five classes. (Or 4.5 classes, depending on how you think of the guardian fighter (sword and board) or greatsword fighter (yeah, thats what they use. There are a couple 2 handed axes and greatclubs in the game, but you're really going to be using a greatsword 90+% of the time). You can tweak a few things, and swap out powers to some extent, but many of the lower level ones are just plain better than others.