Thanks John Saito, This is really helpful — we are trying to decide what is the best option for our application UI!

While reading I have nearly decided that we need to use Sentence case. We want to be more friendly and I don’t need people to feel pain while reading “Take Quick Tour before You Start” ))

But then I understood that Title Case works much better for constructions like “Add Storage”(command) or “Placement Policy”(name of a section) since you can get to second part of a label much faster since you need only a glimpse to understand the meaning. http://www.mrc-cbu.cam.ac.uk/people/matt.davis/cmabridge/ ))

I think that Title Case helps to scan the menus much faster when you are familiar with the subject field.

Compare “Set baseline” and “Set Baseline” if you have “Oh, it looks like I need to change baseline” in your head.

Also in case of abbreviations title Case works much better in the UI, e.g. “Replace VMs”(virtual machines) or “Health of VMs and Hosts” — “VMs and hosts” doesn’t look good to me since hosts are as important as VMs.