Isabelle appears to be everything I usually avoid in an adventure game, yet I'm not sure I wouldn't like to play it.
The graphics are the most obvious negative for me, simple, brightly colored and childish.
The biggest negative for me is probably that the game is not linear. Criticisms that a game is too linear will likely make me more inclined to play it because I don't care for games in which you wander around gawking at the sights and eventually figure out you're supposed to do something, but what? If you look at the games on my list for 2012, it's fairly obvious that I'm never going to vote for Myst.
Keyboard controls...well, possibly. With the obvious exception of my dear Grim, I'm not fond of them and not good at them either. And if I have to put the pieces together from snatches of conversation to figure out what is going on, I'm more likely to be eternally lost than becoming more and more involved in the story.
That said, your review is intriguing. You use words like different, extraordinary, unusual, compelling. It's hard to ignore the impression it made on you.
I once avoided mysteries by Janwillem van de Wetering because of reviews like this one: "He is doing what Simenon might have done if Albert Camus had sublet his skull". Now I'd dig the man up if I thought I could get another book out of him. So, I've learned that the odd, the different, the slightly surreal might be right up my alley. Maybe Isabelle is, too.
My scythe... I like to keep it close to where my heart used to be.