I have a blog post about this very topic saved in drafts. I both agree and disagree at the very same time — that global sidebar is not the best designed thing. I'm replacing it shortly, but not necessarily with something that has labels.
Needing labels is 100% valid criticism, and icon soup is highly confusing to a new user. I can't wait to start testing our solution to this.
I'll throw one into the agreement box as well. LayerVault sounded like a super useful service to me, and I'd been considering checking it out for some time. So I eventually took the leap, registered, put in my cc info and tried getting acquainted with their interface. It was way too confusing for me. I want to use and love the product; I'm convinced it's something I'd find invaluable, but I don't feel comfortable with being lost and wondering what different components of the UI mean/do.
Agree. This was my biggest beef with the Google Hangouts UI until a few weeks ago when they added labels.
At least tooltip them.