Hmm. I'm not sure whether any of these things would really qualify as obstacles in an interstellar journey from A to B.
Asteroid belts as we know them are tiny things; the odds of hitting one en route from star A to star B are incredibly low. Black holes might be big or small, but our heroes have safely flown very close to those things and even gotten out of them easily enough (when lightspeed is no limit, this should be easy enough). And nebulas in Star Trek include almost microscopically small gas clouds (VOY has some that are mere thousands of kilometers wide) as well as larger ones - but ships often sail through the latter sort at high warp easily enough.
Really, Han Solo should have been able to go to hyperspeed in an arbitrary direction without any real risk of ending inside a nova, and Star Trek ships which seem to be much slower and more capable of sensing their surroundings should be able to navigate with even less care.
Then again, Starfleet in the 23rd century did employ dedicated navigators...