Escrito — Collaborative writing with Markdown & Textile

I'm a developer, not a designer, so I would be really glad if I could get some feedback from you, regarding this user interface :-) This is for a simple web-based text editor. Those 3 buttons where adapted from a UI Kit by Raj Ramamurthy (dribbble.com/raj).
Full preview here: http://cl.ly/0J182Z1q241t29471t2L.
Thank you in advance!