Pretty simple; the mouse panning in game is great, but it works completely backwards compared to what i'm used to from panning around images in gimp or any other art program, google maps, what have you.
I guess it can be described as: you have, mouse moves map camera, everyone else does, mouse moves map under camera.
Whoops, not sure how this post slipped by without me noticing xD
No problem, I'll put it in the options.
Shift-panning was originally added as is since this is how it works in strategy games, which was where the original feature request originated, from a player who wanted it to work like that. That said, the implementation is technically more akin to art programs in that the cursor is locked to a given map position (for increased precision), rather than continuing to scroll towards a border.