if you have a slowdown problem you should file a bug report.

uv mapping is totally awesome now in 2.46. it's an area where blender trumps most other applications.

2.50 will be the event system refactoring release which will make everything more customizable. this will also make it easier for the developers to work out some inconsistencies and problem areas in the user interface but altogether there probably won't change that much on the surface. blender will still be blender.