This is definitely a huge improvement. The new bird feels like it’s flying.
Twitter dumped their lettering logo and replaced it with a redesigned bird. Dustin Curtis has a side by side comparison of the old and the new one. Sure, the latter looks more like it’s flying, but I think the old one looks nicer.
In my opinion the new one looks more heroic whereas the old one looks cuter. However, here is a short description of the new twitter logo by Doug Bowman, Creative Director at Twitter.