It depends on the venue. If you have a proper studio grid, then your main problem will be sight lines - ie the actors will have their backs to large percentages of the audience at certain times.
As far as technical wise:
Lighting is not 'difficult' but a fair bit of thought is required - back lighting, cross lighting etc are essential, as there is no true "front" and "back" of the stage.
Sound is where it gets a bit more technical if vocal reinforcement is required. In a standard theatre, you essentially have a point source (the stage), in an alley configuration, you have a source that runs the entire length of the venue. It feels really odd if you have a mono sound rig in this sort of environment, for best effect, the sound needs to pan across the space as actors walk - and there are 'issues' when it comes to speaker placement - as a single PA will not really work, you really need 2 PA's (one for each side).
There are plenty of challenges, but none are 'difficult' to solve, they just require a bit of thought.