The secret of the Gorillapod's flexibility and grip is the construction of its legs, which are made from linked chains of nine ball-and-socket joints. The joints are individually very stiff and difficult to bend, but the leg as a whole is extremely flexible and can be bent into any shape quite easily. Each link has a thick rubber ring around it, so when the leg is bent around an object it grips with multiple points of high-friction contact. With three legs wrapped around an appropriately sized object the grip is surprisingly firm.
Obviously with such a complex structure the main concern is going to be durability, since each leg has at least nine possible failure points; however I've put a Gorillapod Original through several months of fairly vigorous use while testing compact cameras, and I can report that it's showing no signs of wear and still grips just as securely as ever. I've also used the Focus for a couple of weeks, and so far it seems to be even less likely to break.
The Gorillapod Original and Gorillapod SLR have two extra links above where the legs meet to provide a bit of extra flexibility, and give the option of positioning the camera horizontally while gripping vertical objects. They also both have quick-release camera platforms. The SLR-ZOOM and Focus sacrifice both the extra links and the quick-release platform in favour of greater strength, with the legs attached directly to the camera platform. However the Focus does come with an adapter converting its standard ¼-inch tripod fitting screw to the larger 3/8th-inch screw used to attach professional tripod heads, so you can use it with your favourite head for extra flexibility.
There are a number of accessories available for the Gorillapod range, including spare quick-release platforms for the Original and SLR models, and some vicious-looking spiked feet for the SLR-ZOOM. All Gorillapod models and most of the accessories are available in either conventional plastic blister packs, or in eco-friendly recyclable cardboard packaging for a few pounds less, which is a nice idea.
The Gorillapod is an ingenious and highly effective lightweight alternative to a full-size tripod. All the models are exceptionally well made, highly portable and offer an exceptionally versatile means of supporting a camera in a wide variety of situations. They are a bit on the expensive side, but are well worth the money.