I love trying new things and I love learning new software but I've learned the new gmail UI and I don't like clicking 2-3X more for things I do pretty regularly. Like getting someone's email address.
People have to get that it's a product for many, not for all. You can agree with hiding emails or not, but a company as large as Google wouldn't hide it just for the sake of it. Obviously there was research and data that backed that change.
Bottom line is, if it was your company, you'd hide stuff to improve the experience of 90% of your customers at the cost of a few without another thought.
Breaking Gmail for business users doesn't seem like a good idea since they are the ones who are actually paying for the service.
Or any other mail client?
Unfortunately it involves running a program on a PC and the PC is dead. Nobody uses PCs any more. Didn't you get the memo? :-)