It will do the job of a tripod and the lightweight construction means that it really is effortless to carry around. However you don't be using anything heavier than a 70-300mm budget line lens on it. For light lenses its ok, but don't leave it freestanding in the wind nor expect the same level of stability that a heavier set of legs would give you.
Also note that you can only go down so far with them, since the legs cannot be splayed out.
I used to use one (till I broke it - tip - never unscrew the panning arm on the head - they never go back in right) with my 70-300mm sigma and it was a joy to use for the fact that I could walk with camera and tripod in my hands bolted together and deploy the tripod ready for use in seconds. Effectivly it was like a 3 legged and more stable monopod for me in how I used it; but I also used it for macro work as well as regular static shot, longer exposure stuff.
In the end I've upgraded to a heavier set of legs that offer me far more versatility, if losing the lightweight construction aspect.