I really like the Gitzo tripods. In fact, I have three of them!! I have a little 200 series aluminum unit that's small enough to pack into a suite case for air travel, and works fine as long as you're not using it to pan a 300mm f2.8 around. That one has a Gitzo ball head on it. I have a 300 series Gitzo aluminum model that's my work horse. It has a three axis pan head on it, which is critical for using long lenses. With that, I can do a 10 second time exposure with a 300mm f2.8, so it doesn't get much better than that. I also have a 400 series aluminum tripod that's pretty much been retired since I packed up my medium format gear for good.
If you're using long lenses, get a 3 axis pan head. That way you can pan from side to side, or up and down, but still keep the rotating axis tight. There's nothing worse than putting a big lens, or view camera, onto a ball head, and having the whole thing fall over on it's side. Ball heads are good for general use, and with only one control, are a lot easier to use.
I have a 500 series aluminum monopod that works great. I only use it on the 300mm F2.8, and I don't use any kind of head on it.
Carbon fiber is great for saving weight, but it's not as sturdy as aluminum, and if you ding carbon fiber, it seriously weakens the tripod. If you're out hiking with it, by all means go for carbon fiber, but if you're like me and the tripod spends most of it's time rolling around the trunk of my car, then aluminum is probably a better choice.
David Buzzard's Technical Blog