[Zeke]

No, it's not consistent. Warp within a solar system is sometimes treated as dangerous to add a little tension, but more often it's not (how many times have we seen characters on a planet's surface watch a ship go off into warp?). However, even if full impulse is only 1/4 lightspeed, that's still pretty fast for intrasystem travel. It would get you from the Earth to the Sun and back in just over an hour. That would be more than fast enough except in emergency situations -- it's sure a lot faster than we can manage now.

If I recall correctly, the two series that made the most use of this no-warp-in-solar-systems rule are TOS and Enterprise. If that's true, then another explanation is that warp technology, like any form of transportation, is continually being improved to reduce dangers like this.

My technological pet peeve is intraship transporting, which is supposed to be more dangerous than regular transporting. Why? It should be much safer -- the computer knows the ship's precise layout already.