JOSM should not make me wait for up/downloading data

[xeen]

Downloading or uploading data makes you sit in front of a progress bar with nothing useful to do. I'm not sure if this is avoidable for "normal data" because of collisions (i.e. uploading data, while editing it.), but it sounds safe to implement this for the GPS download dialog.
Only problem with "hiding" the dialog is that there's no place to display an error message if the download failed, and popping it up from nowhere doesn't seem too good either. Maybe displaying a note in the "map area" might work, at least it shouldn't take up any permanent place.