Architect Walter Croft uses AutoCAD LT 2010, and he knows how to quickly — and easily — change the shape of a hatch.
"After fighting with the Hatch command many times, I found that instead of re-hatching an area, I could change the hatch area by adjusting the grips on the hatch to either fill or reduce an area previously hatched."
Notes from Cadalyst Tip Patrol: Hatching has really improved in the past few releases of AutoCAD. In AutoCAD 2011, you can grip-edit your hatch as Walter describes. Select the hatch, pick a grip, and move it to a new location.
You can also pick the midpoint grip for more options. Hover over the midpoint grip of a hatch and you are given these choices: Stretch, Add Vertex, and Convert to Arc. (It's the same for a polyline.) These are great tools for editing a hatch. Stretch will, well, stretch that leg of the hatch. Add a Vertex will add a new vertex point, which gives you great flexibility; you can make small changes quickly without having to recreate the hatch. The Convert to Arc option will change the lined edge to an arced edge. If it is already an arc, you can convert it to a line.