Upload & Sell: On
In general, the more sections it has, the shorter it is when "closed". This can be important if you want to travel with it. Carbon fibre pods are nice, as they're relatively light and not so cold to the touch for bare hands. OTOH, a neoprene grip section at the top of the monopod is always welcome. I can't say that I've never used a monopod to help with balance, but I would certainly not use it as a walking stick while hiking.
I highly recommend the Feisol CM-1471 carbon fibre monopod. It's small, light and relatively inexpensive ($128 at B&H). It's great for general purpose use, including travel, and it can easily handle lenses up to and including the 600/4L IS and 800/5.6L IS (which is lighter than the early 600's). Unfortunately, it can't handle the Canon EF 1200/5.6L or Sigma EX 200-500/2.8 APO IF HSM...
Depending on what you're going to do with the monopod, you might also want to consider a monopod head. This lets you point the lens up and down without having to lean the monopod a lot. Note that in order to point a lens up, you need a relatively long monopod, and the head helps a bit with this. For lens weights up to about 1.5 kg, the little Manfrotto 3232 tilt head works fine. For heavier lenses, the RRS MH-01 is the ticket. I have both.