Yes is a deal breaker without this feature. You need a PC based Thunderbird account or webmail based account to create IMAP folders first. Not found a mobile based e-mail app that doesn't create IMAP folders, only K-9 and now Thunderbird have this fundamental part missing.
Yes, folder creation is an essential part of email management. If I have to do that from my web-based platform only, I lose out on lots of productivity. Let's go!
Yup and edit the name of the folder, delete and sub folders. This and being able to move emails from the unified folder (already created a feature request for this) would make the app complete for me.