There is a lot of info on the web from a lot of dedicated hammock campers. Ditto on HammockForums, it's great. Also,
Just Jeff's Hammock Camping Page is the best general introduction I've found, very readable, with lots of links. There are also a number of threads on ETS.
I have a Hennessy Explorer Ultralight and like it a lot. I got the undercover/underpad, which I need whenever it is even slightly cool. Hammocks are definitely cooler than ground camping, which is fine when it is hot and muggy, but worse the rest of the time. A slight breeze comes and I instantly feel my bubble of warmth float away. I'm saving my money for an overcover and an underquilt/overquilt setup, I hear that is the most comfortable approach.
It is a good idea to have a backup plan in case you get too cold and have to hit the ground, such as a closed-cell-pad. And I would not plan to use a hammock in any weather in which I have not already tried it out in my back yard. I'm a relative newbie but have the bug bad.
Overall, I'd say hammock camping is not so much better or worse than ground camping, as it is different. Different benefits, different disadvantages.
Steve