Personally I am a big fan of the new compose, although I can also understand why it isn't right for some people.

My usage would be something like 80% very short emails, 5 lines or under with maybe a copy paste block. Occasionally I will want to add an attachment or a cc.

The speed and the ability to still see the email list works for me. I should also add the majority of my gmail use is done on a 27 inch screen.