The killer feature is the editor knowing what's going on in the image. For example typing (blah - he can check from the current package - whether that's functio

The killer feature is the editor knowing what's going on in the image. For example typing (blah - he can check from the current package - whether that's function, special symbol, etc. - and if it's in a table of specially formatted ones (if, when, unless, etc.) it can do better formatting. Not only that but you can inform about this in the actual. Same goes for Lispworks, and maybe for AllegroCL. Difference is emacs communicates with slime to the swanked image, and if that image hangs, your editor is still there - not the same with LispWorks and AllegroCL (but if you are careful, and know when it can explode then it's ok).