I would like to try Sketch. This are the issues I have faced.
1. I have cloned the git repository and imported the project. Great.
2. I see a bug (if the Control view is not open the Free Sketch tool is not working). I am trying to report this but the link to Support on the main page (http://www.eclipse.org/sketch/#) is not working. I have seen a number of other problems that I would also like to report and even fix, but I could not.
3. I have tried the "Getting involved" link on the main page. The "git clone git://git.eclipse.org/gitroot/sketch/org.eclipse.examples.co re.git - the Shapes example application" link is not working.
4. The "Documentation", "Download" and "Support" links on the "Getting involved" page are again not working - 404.
5. I have tried getting to the state shown on the clips in youtube like http://www.youtube.com/watch?v=bRd8bVakmUI, but I was not able. I suppose much of the code is not submitted or is just not "accessible".
I think you have a good idea with Sketch. (and some great mentors on the project) But currently I can not get it running as shown in the clips and I can not effectively collaborate with you.