No downsides. All your mail is downloaded locally and off line available. Fast Search with mu.

Really if there is one thing you should do this year is take some time and discover emacs. Just for orgmode alone. You will Thank me later :-)

In a nutshell: Emacs is a machine. A lisp machine. It will work for you instead that you work for your computer.

It will do anything you want ( and more)

Now is the time to discover this shining gem in all of softwares.

Ok, you got me. I'm going to give it a shot. :-)