Something that I have been wishing to have for quite awhile is the ability to adjust the mouse speed. Esenthel's mouse speed overrides windows' mouse speed settings. The Esenthel mouse speed is very sensitive and very fast. It makes it extremely difficult to do very precise object placement as you can't move an object or scale an object by a hair. Just the slightest touch of the mouse and it moves a considerable amount of space and very fast. It makes it very difficult to do intricate object placement. So I would LOVE to see something that allows for mouse speed adjustment!
Also, This may sound petty but for me, at least, it would be very useful. I'd imagine others would find it useful, too.
When you select a group of objects (say a sconce, torch, and flame particle object) and insert them as a duplicate group of objects, it would be extremely helpful to be able to move the group, scale the group, and rotate the group all together at once as though it were a single object. Currently you can move the group but with very little control and you can't make it as precise as you can with a single object.
I prefer using the arrows and mouse to move, rotate, and scale my objects as opposed to entering numbers. It's just easier for me to place it more precisely. So being able to do this with a group of objects (like the sconce example) would help so I wouldn't have to move each individual object in the group.