I'm with Sacriven. Some images are quite large, which makes it difficult to tag on my tiny laptop screen ... :( Not always, but sometimes the uploads interface shows the full size anyways, even if I haven't detached the upload box. For those times, I add as many tags as I can remember from the picture before uploading, and then use the posts interface to add the remainder since it defaults to the nicer presentation of fitting the images to my screen if necessary...
In addition to what Sacriven said, it would also be nice to set the default size on the detached upload box, for both the uploads interface and the posts interface. It needs to be widened quite a bit to get an easier access to the Related Tags, Frequent Tags, etc. I can do this every time, but it'd be nice if I could set my own default instead of using the system default.