Here's my design. I made this thinking aimming for better usability, after reading some posts here I saw that:
 
1. The 'launch' is the most important action for this launcher (duh), so i moved it to the top left, right under the user profile for
quicker access.
 
2. The tabs on the old launcher took a good amount of the screen, so I moved it to the side and made it smaller for better view and distribution.
 
3. Lots of text and scrolls in the mods/maps/textures sections (the descriptions took about 1/2 of the screen, but only uses 1/3 of its space and create a long scroll bar), most packs have the same icons, only changing the text and unintuitive sorting options. So to address this I changed the least used options to icons, so they dont have the same weight as the most important ones. Put a banner (maybe with screenshots) on the description pages and moved the 'mods included' to a table for easy checking the contents and less scrolling. Also 2 types of layout for this page, the 'full layout' is the one in the image and the 'thumbnails', with only the thumbs for each pack for faster browsing.
 
3. Added a 'toggle console' embedded in the launcher, so you don't have 2 separate windows and can quick hide it.
 
4. Less gradients, shadows and textures. Skeuomorphism is getting old and users don't need a '3d' look anymore to know what's interactive and what's not. The flat design gives focus to what's important: the information and not the UI itself.
 
So what you guys think? Give me your feedback!
 
OBS.: This is a rough wireframe, the colors and icons are 
not final. I'm also changing the ftb logo.