First off, I'm not saying that the feat isn't useful; it is, the flaw is not that limiting. But most people who talk about it on these boards seem to forget one thing:
Sculpt Spell only alters the area of a spell. It does not modify range, and any part of a spell's area which exceeds the range is wasted. So a spell which has a puny range, such as Burning Hands' 15 ft, could be sculpted into a 40' cone, but everything beyond its range of 15' is wasted, ie. does not hit anything because the spell is forced to end at the 15' mark.