I've used the free version for over a year and briefly tried the paid version, but ultimately reverted to the free platform. I find eM Client a nice, well-rounded and customisable choice of email software; nothing particularly special.

It's easy to use. It can connect to a variety of different accounts. It has a calendar interface. It connects to other messaging apps too.

nicer look and feel than outlook, feels much more mature than gmail or other web clients. I used this for gmail and outlook accounts; google email,calendar and contacts with only email for the outlook.com account. unfortunately my work security rules prevent its use on my work account. i would love to see what a mobile client from emc would do!