Designing a background for Twitter can be a pain sometimes. Fuel Your Creativity has taken that pain away with this very resourceful Photoshop Template.
Tweeting from Apps
I must say, being able to tweet from apps on my computer is pretty awesome. It makes posting videos and pictures very easy which in turn makes my work easier.
Also, when you have clients that you have to post pictures and videos daily for, the ability to add multiple accounts is genius. just makes it so much easier to do it in house. I think for this alone, upgrading to Mountain Lion is a must.