The persistence bit is a nice idea, used in other games including Fallout 3.
But the problem is that you could, basically, go through the game without levelling (if that was possible) and still only encounter suitable challenges.
Then again, as long as character builds are non-linear and unpredictable, it should be possible to achieve a sensation of power earned.
However, based on the CharCreator - it seems to me the builds are relatively straightforward and linear overall, so my guess is that no matter what you choose, you'll end up with a capable character. They apparently didn't feel multiclassing was worth keeping from D&D - which tells me it's not what I'd prefer.
Essentially, it seems the only real challenge is in a tactical sense, meaning in HOW you fight. Strategic challenge, as in how you build and plan your characters will likely have much less of an impact in terms of overall capacity.