I have WP 3.1 and the plugin work well.
Was the only plugin that can put "image watermark" and work! (other only put text (and need some librarys) or say can put images as watermark but not do it)
The only bad point is "the watermark is not automatic, is only manual", that is the bad part, but if you click in "watermark > select all sizes > apply" the image will have a graphic watermark. Maybe in the future can put this automatic for make more easy and faster the upload of the picture with an automatic watermark.
Thanks for this great plugin. Thanks so much.
p.s.: Sorry of my bad english.