I purchased a new Apple MacBook Pro 15.4-Inch Laptop with Retina Display late last year, to replace my EIGHT year old Macbook Pro 1,1. After using the new one for several months, I don't know how I managed to tolerate using the old one for so long. Everything on my new Macbook Pro just flies. Well, almost everything.
Mail for OS X Mavericks always seems sluggish. For an app that I spend way too much time in, it's frustrating to have to wait for it to keep up with simple things like replying to an email. Disabling animations helps a little. I downloaded this plugin that disable's Mail animations and now Mail now feels a tad bit quicker.
I hope Apple gets to working on making Mail more responsive in future updates.