I only have experience using the Sony wide angle adapter, part
#VCL-HG0758. I use it on the PD170 all the time but I also use it on the GL2 because it's the same filter thread size. Overall, I can say that I'm very happy with the performance of the lens although there is some distortion with vertical and horizontal lines, but it's not distracting. The Sony lens is a .7x, which means it's a totally zoom through piece without loss of focus, also giving you a 30% wider field of view. For the price, this lens is hard to beat.
I'm sure the Century Optics adapter is a better lens, without the above described distortion, but it is a substantial increase in price.
- Don