Some of my rants on Usability.
1. Drag and drop should not be the only way to do any function. Drag and drop is an extra convenience—good design should allow for accomplishing all functions easily without it.
Drag and drop is arguably conceptually usable. But physically, it's hard on the fingers/hand/wrist. Also, the mouse is generally imprecise.
2. Design for keyboard use first, good mouse use will generally follow. All functions should be able to be accomplished via the keyboard alone without a mouse. Making it easy to do by the keyboard often results in making it easy by the mouse as well—or at least giving a good headstart in that direction. Doing the mouse case first can make it miserable for the keyboard case. Although one could make an exception for certain drawing programs, I have long wished that drawing programs would allow me to insert objects/items and specify the location by number, and nudge them in various directions with the keyboard. It's far more accurate than using the mouse and often faster/easier.
