Seems like the Gmail team just pushed another phase of their UI update today (for Google Apps users anyway, not sure if standard Gmail users had this already). All buttons are now using custom graphics and the tools have been clustered in a far clearer way. This is an additional update to the already pretty substantial refresh the interface got a while back (with skinning for standard Gmail users). See the screenshot of the new sidebar. I love it. Simple, Googl-ish but not ugly in any way.

I like where Google is going with this. Gmail's UI team was quite ballsy when they decided to rethink the way mail/webmail should be interacted with and shunning many of the convention set by its predecessors. There was a learning curve but I really couldn't go back to a 'normal' e-mail client today. This update tweaks some of Gmails weaker UI points.