My friends list shows those online (in alphabetical order) on top. Check that you haven't got "Sort by name" ticked when you click on Friends in the title bar.
As for your most played games, you can assign them into your own custom made category by right clicking and selecting "Edit...
It's definitely a very nice and long past due update to the UI, it'll take me a bit to adapt to using it. Only thing I miss is the Obsidian skin, all this grey... blargh.
Valve has just released a Steam update that supposedly fixes offline mode which also purged quite a few people's friends list. This could be a side effect.
Yeahhhhhh, you're pretty screwed. Steam games are irrevocably tied to one account, so you got gypped for buying it second hand. If you've got the cash, Orange Box is a pretty good (and cheap!) deal.