Rated 2 out of 5 stars
Agreed with Mel -- it's almost useless. Unfortunately.
1. Only context menu, no any "highlight mode" nor even toolbar button
2. No persistence or even bookmarking etc. (look on LiveUrls/WebMarker)
3. Only F2 movement btw marks, no visual indication that any other marks not inside viewport are here
Of cource this is small and not overbloated like Diigo or Wired and still useful for a one-time page "painting" (preprint for example)