The pictures he posted were not only demonstrating a much wider angle of vision but also a much better image quality than with the original lens (in the case of the Foscam fi8908w). So it convinced me to do the same.
I bought a 2.1mm 160-degree lens from DealExtreme.com (M12x0.5 thread) (same can also be found on eBay) which finally arrived today.
The procedure below applies to many other ip and web cam models, as long as they use the M12x0.5 thread standard. It can of course also be used with other 2.1mm lenses if you don't want the fish eye effect. DX also has a 6 lens pack deal ranging from 2.8 to 16mm. They can be fitted but their lens ring is of smaller diameter than the hole in the casing, so, beside being unsighty, it will also allow dust to get in the camera.
First, a small disclaimer: this kind of change, even so small will not be covered by your camera guarantee, and I won't send you any of mines if you screw up!
The first thing to do is to unscrew the original lens completely.
First, as the thread is super-fine, make sure that you don't force it while screwing in.
Then, once roughly in place, you should re-connect the camera to do the fine-tuning with the "Live Video" page open.
Once in place, not only the field of vision will be much larger, making the PTZ function almost un-needed, but you may find that the image is also much sharper and brighter.
Below are comparative examples (click to see in full size)
There's been reports that some lenses would get blinded by the IR leds.
I didn't have that problem with the sku 15237 from DX, so just make sure you buy lenses with IR filters.