Love this tool a lot :)

Pros:

• Straight forward UI that everyone can just use with no learning curve at all
• Fast loading and no dependency on any 3rd party plugins (no installation)
• No signup, simply doing the job correctly

Cons:

• Not many options (image size can be too small for high resolution use)
• You should upload image with exact ratio (no gravity zoom supported)
• Website rendering would be a really good add-on feature