I did not know how dirty my lenses were until I used this product.
The pen looks and feels quite tacky but it is a great piece of kit which now goes everywhere my camera bag goes. Its overall size is quite compact. At one end you have a retractable brush which is great for flicking dust and dirt off lenses and cleaning out the threads, where mischievous particles can lurk. I found it most effective to use the brush in combination with a blower.
The other end of the pen is a soft pad which is dabbed in some sort of cleaning agent held in the cap. This can be used to wipe clean smears and stubborn dirt from the glass by making small circular motions, like a spirograph. On one occasion I found the pen left a trail of tiny dust particles but I simply put the cap back on, gave it a half-circle twist, and tried again. The dirt vanished very quickly!
The pen is versatile and I have successfully used it to clean the lens on my camera phone, as well as various LCDs and touch screens. It does not appear to have affected the coatings on any of them.
One note of caution... the brush is some kind of nylon or other artificial fibre. I would suggest that you never attempt to brush your DSLR's sensor with it since there is some potential for static discharge.
All in all, this is a great product. No worrying about cleaning solutions, and at least as effective as a lens cloth. Highly recommended!