I have one and don't use it that much but when I do it seems to work very well and is very portable, they are strong and well made. The downside is making sure especially when shooting from above the height of the tripod that there is something to sit it on or attach it to, I guess it comes down to why you want a tripod i.e. what scenarios you will be using it in.
If you are looking for something compact and portable then I have just got myself one of these (ultra Rexi-L) it is more expensive than the Joby doesn't include the head but is collapsable down to 36cm and will go a lot higher than the Joby of course.
I guess it comes down to why you are buying it personally I have 3 tripods and a monopod depending on what I am doing and where I am going a manfrotto 055xprob is my main tripod, the Velbon Rexi-L and the Joby.
Whilst the Jobby is a nice price I guess you need to think through what you want to use it for and if it is up to the job. Just trying to give you some food for thought