Thanks, I hadn't seen that one before. :)
Yeah, it's a similar concept, as is http://mlkshk.com/ with their new bookmarklet.
I think two things set imagestash apart:
1. The bookmarklet has many more features, and works in more cases. You can use it to snag multiple images at once, view any images on a page as a slideshow, expose images obscured by CSS or Javascript trickery, find full size images from thumbnails, or download a batch of images directly from their page as a .zip.
On browsers that support <canvas>, it will even get images behind a login wall where the server can't download them directly.
2. imgfave, mlkshk, imgur, etc. are all geared toward sharing first, and private collections second, if at all. Imagestash prioritizes the other way -- building your own collection is the primary goal, and sharing publicly is secondary/optional.
