"A form but­ton that says Sub­mit gives users the impres­sion that the form isn’t focused on a spe­cific task. It also gives off the impres­sion that your web­site is not user-friendly because you’re speak­ing in a tech­ni­cal way that most users aren’t famil­iar with. If this is the impres­sion your users get when they fill out your form, you can bet that you’re los­ing a few users in the process."

http://uxmovement.com/forms/why-your-form-buttons-should-never-say-submit

This is nice: Showing the user's avatar after entering username.