Looks interesting. I have tried to use a few annotation tools before within the team but people were more comfortable and accustomed to emails and we ended up switching back.
This looks like a perfect solution
Trust is something very subject but they have been in the industry over a long time. Box was started before Dropbox in 2005. It has been focusing on enterprises till now.
I guess with the new iOS app and free space they are planning to move to the consumer market.
I loved the way you guys presented the simplicity of the app above the fold itself!
I agree that there are lots of players in the space and adding to the list given above, namely, Easyproof, Proofhq, Pixelapse and Conceptshare come to mind. Also, there's Framebench that's making some noise with its novel real time functionalities. I really think they might have something there.