I bought 2 of these for mounting speed lights for photography. They're very well constructed, considering their size and weight. I think they're limited to 2kg payload (say Manfrotto). I'd say that's about right. If you put more than that, with any kind of boom for leverage, things will start to flex quite a bit.
Obviously they don't have the same feeling of stability and strength as their bigger siblings, but they are considerably smaller when folded down than even the next size up. These are manageable to carry on your own. Those might not be.
Buy these if you like to travel light in every department. If you regularly use heavier lights you'll need something beefier. More weight, but then, you're carrying those heavier lights anyway.