I have the Sony VCL-HGD1758 1.7x Tele conversion lens. This is a very nice lens for this camera. I have taken some really nice images with this setup. There are two drawbacks to it, 1) its a heavy lens when on the camera, so you need to use it with a tri-pod and 2) is that with the tele on and the camera at wide angle, you get some venyetting of the image. i like to use it past that, to full tele with digital zoom.
I have read some other lens might not work correctly with this carmera.