I'm not sure whether this is a bug or a possible feature addition, so it's going here instead of Mantis for now.
No scaling is applied to the mouse cursor in nonstandard resolutions, so it looks quite small compared to everything else with large resolutions. This is probably just a bug. The main issue though is that the mouse sensitivity is effectively decreased when the resolution is increased, since the distances (in terms of the displayed pixels) between buttons and other things have become larger. Is it possible to have the game compensate for this by having some kind of sensitivity multiplier that changes along with the resolution, or at least allow it to be specified through a command line option? I have the ingame mouse sensitivity setting at its maximum and it's comfortable at the standard 1024x768 resolution, so it won't go any higher than that and moving the mouse around in a higher resolution feels very slow.