Vialogues (= video dialogues) lets you upload your own videos as well as use videos from Youtube. Uploading videos the file formats supported are: .mov, .flv, mp4, mpeg, and .avi. Other formats (such as .wmv) will be supported in the future.
Questions can be posted at certain points of the video (like Grockit Answers) and the range of question types includes multi-choice (poll) as well as open-ended (text) questions. You can also delete the questions and answers if you want to do that.
Unlike Grockit Answers, the video doesn't automatically pause when you start typing a question or an answer.
Private weblinks are created if you want to restrict your questions/answers to a particular group. Not so easy to figure out how to get to your own created vialogues - you have a list on the right side of the screen under My Vialogues when you log on initially, but after that it's not obvious how to get back to it - however clicking on your name/view profile works.
A plus for Moodle users is that it is easy to copy and paste the embed code to embed the Vialogue in your Moodle LMS course - Moodle participants still need a Vialogues account to see the Vialogue activity.
My rating: 8/10