If they do it like a western with Obi-Wan as a reluctant hero forced into action by his own morals it could be really great.
I always found Obi Wan's adventures in the prequels boring, and to be the points where the movies dragged the most. I personally shudder at the prospect of an entire movie of same, particularly based only on Tatooine. His character is a mystic sage, not a noir private eye.