I felt the same way at first. Once I got used to it and learned my way around, it isn't all that bad. One great feature is reading messages in the expanded mode without having to open each one. The greatest thing is it essentially stops most all the spam. The treads are harder to follow, however. You can ignore/un-ignore people directly from the posts (but why would you want to?) without having to go and un-ingnore your whole list.
I don't like how it keeps the last thread posted on top, not the last message posted which essentially pushes popular conversations lower while keeping pointless topics (which some will think this is) from falling lower as they should. As for expanded mode (my settings always keep it in expanded mode) so that doesn't effect me... I could deal with spam, just a minor thing for me, but does it take away the ability to post links (I consider this another downside)