I use a Manfrotto 681 (the 681B is the black version) and absolutely love it. It is sturdy and light and will compare very well with the much more expensive carbon fiber monopods. YES, I would purchase the black 681B if I were buying today but it was just not available when I purchased the 681.
http://www.amazon.com/BOGEN-681-B-Manfrotto-Monopod-Camera/dp/B00006IS2W
One reason that the 681(B) is light and sturdy is because the 681(B) is a three section (rather than four section) monopod. However, the drawback to a three section pod is that it doesn't fold as short. This may or may not be a problem for you.
I like a quick release clamp to adjust the monopod leg because I use it like the monopod that is shown in this youtube video. A twist release would not be as easy to adjust.
http://www.youtube.com/watch?v=Pth9aKWh3Go&NR=1
I DON'T USE A BALL HEAD ON A MONOPOD!
1. If you are shooting with a lens which is equipped with a tripod ring, the ball head is not necessary. A simple Manfrotto monopod tilt head will do very well and is lighter and less expensive.
http://www.digitalfotoclub.com/sc/from-froogle.asp?id=964749955&rf=froogle&dfdate=5_1_2009
2. If you are shooting with a lens which doesn't incorporate a tripod ring, then use a Kirk MPA-1 which is the Manfrotto Swivel Tilt Head with a Kirk Arca Compatible Quick Release System:
http://www.kirkphoto.com/tripods.html#monopods
An Arca Compatible Quick release System allows the use of either a Kirk or Really Right Stuff L Bracket when shooting with a camera/lens that doesn't have a tripod ring. The L bracket balances the camera/lens atop the monopod when the camera is in the vertical position rather than hanging the camera/lens cantilevered over to the side.
http://reallyrightstuff.com/QR/05.html
BTW: The Arca Swiss Compatible tripod/monopod mounting systems are expensive but, they are well worth it. Once you start using this type of system you will wonder how you managed without it for so long.
Really Right Stuff also distributes two types of monopod swivel heads, which look very interesting (especially the MH-01), although I have had no specific experience with that type of head. I would be willing to bet that these heads are very good since every piece of equipment I have seen from RRS is extremely well made.
http://reallyrightstuff.com/search....ORID:11&ie=UTF-8&q=monopod+tilt&sa=Search#926