On Windows I really liked IrfanView as a basic image editor/manager.
Some of the main features I liked were
- great shortcut keys
- good batch conversion options
- ability to work with many image file formats
- easy viewing of images in a folder
- ability to open the program and paste the clipboard and do a quick save
- simple cropping
Though it did have a lot of features, they tended not to get in the way of simple tasks.
What would be a good replacement on Ubuntu?