easy to use, brilliant for clients
1 - Responsive images for multiple devices, exactly as described.
2 - The add-on resizes the images for you and makes them the 'right' size for whatever container they're in. This is brilliant for clients - they can just upload and all the resizing is done for them. You have universal control over the sizes of the images through the dashboard presets (paid version). Very very useful.
Support was quick.