Early "first night only" verdict?
I'm aware that Conan sucked on his first night (heck, his first year) too, but even still... something about Fallon just SCREAMED "trying too hard".
The Roots were great though.
One big thing Fallon can do right away? Fire that really lame announcer. Second? Stop playing with Twitter (I've read a few blogs and posts around the net from people who were in the live audience yesterday and they say he was peering down and typing like mad on his iPhone during every break, and even during the musical performance) and pay more attention to your live audience.