If you want to have rock-solid ball-head when you're on the go this is the only unit to consider.
I think for the money this is a superb piece. The big knocks on it seems to be the need to orient the base of the ball-head to access certain angles, and a limited amount of creep when tightening.
It can be annoying to have to rotate the base of the unit to access certain shots, but in all honesty it isn't a deal-breaker for me. It's one of those things that you just plan for when you setup your tripod. Now that I have gotten the hang of it I rarely have to reorient the base when going from landscape to portrait.
What people are forgetting is that the design actually gives you MORE freedom of movement than a traditional design will. I find it very useful for macro work.
The other knock is the creep when tightening. Now this IS an issue I suppose. The key to minimizing this is to keep a certain amount of tension on the ball as you are composing. The movement is SO buttery smooth that you can do this and there is no difficulty in framing your shots. In fact, even if you have it locked all the way down and lean on it, it's still buttery smooth. This thing is basically VERY smooth to operate.
Hey so you have to learn a little to use it, it's the most capable light ball-head on the market, and while some complain about the limited angles, you actually have MORE range than you would with other units.
Again its all about what you take pictures of how you like to take pictures that should determine whether you purchase this unit.