I don't know about all the collaboration and sharing hoo-ha.

I can say though that when I'm doing front end development I waste alot of time iterating on user interface changes by changing the code and building the app and running it.

I try to reduce this by doing live CSS tuning as much as possible using Chrome developer tools then I move my adjustments into my code.

Something I have thought would be helpful would be a tool that displays all the colors that I am using on a page and allows me to easily change them.

Also to be able to list all the fonts I am using on a page and rapdily find the best looking font by allowing me to cycle through different fonts.