I'm not sure about the level difficulty. In the original Kickstarter video, InXile CEO said, with some conviction, that this will not be an easy game. That, and the history of Bards Tale games being difficult, convinced me to spend an extra $12 during the kickstarter campaign and buy the Strategy Guide too. Turns out, I didn't need to as InXile is giving everyone who kickstarted the game the Strategy Guide for free. It's 138 pages long (per a Brian Fargo tweet....I haven't received it yet).
I think the game will be difficult in that you can go into areas you shouldn't belong in and get your ass kicked. Early in the development they talked about level gating by enemy difficulty. While it's a linear game, there is lots of choice. You can go down into a dungeon and find yourself overmatch by enemies. You might need to come back when you're stronger. Or maybe you get lucky (or are very skilled) and improbably win the battle. You'll get rewarded for that.
And there are also supposed to be challenging puzzles. The type where, the clues for solving are scattered around other areas and you have to pay attention to the pieces and put them all together to solve the puzzle.
Game releases tomorrow, but as excited as I am for it, I probably won't get to dive in until November (work/life gets in the way of fun).