Summary: If you want an objective review - this is it. I can afford to be fully objective .... because I did not pay a lot for this teleconverter. In fact I bought this genuine Canon item along with the adapter mount all for about 1/10th the cost advertised elsewhere. Therefore, with only having paid out a little, there is no tendency for me to 'over play' the performance of this converter.
Summary: I purchased this lens several years ago now. It is never removed from my camera unless I have a close up picture to take. On close up pictures a lens circle will appear on your pictures if you do not remove. The lens very quickly and easily clicks on and off without effort. The lens is great for bringing distant items into clear focus. On max distance you do need to have a steady hand to obtain clear pictures. If I lost my lens I would buy another one in a heart beat.
Summary: This is a great tele converter. It does not slow down the the auto focus. It works with longer focal length. Shortest focal length will produce vignetting BUT tele converter is designed to maximize the focal length, so when you need shorter focal length, take it off from your camera to avoid vignetting (dark corners/tunnel like effect).
Summary: I purchased the Canon TC-DC588 Tele Converter Lens and adaptor to use with my Canon Powershot S5IS camera to take on my "dream vacation" to Alaska. I found the lens quite handy for taking close up views of scenery and wildlife. It was somewhat difficult to use the teleconverter with the LCD focus because I had too much "camera (or hand) shake" to obtain a good focus. I had better success when I switched to viewfinder focus and could brace the camera against my forehead.
Summary: I have been using the TC-DC58B teleconverter on my Canon Powershot S5 IS for a couple of years using the LA-DC58E conversion lens adapter. Compared to some other alternatives I was shown this gives excellent results. Any adapter that doesn't fit perfectly, i.e. shows play at the joints will be useless. Even working without a tripod with full x12 zoom, in good light, results can be obtained that approach professional 300mm lenses on expensive SLRs.
Summary: Warning: DO NOT ORDER THIS LENS FROM NWV DIRECT even though it is advertised as slighly less expensive. NWS DIRECT is running a scam. They will call you the next day to let you know that this lens is on backorder for 12 weeks in the entire country (a bare face lie) and then insist on sending out a 'better' Canon substitution for anothe $[...]. This substitute is in fact not from Canon, but an very inferior Optics lens.
Summary: I purchased this for my S3 IS. You will get tunnelling if you don't use this with the zoom fully extended but that's really what its for. It brings those distant targets just that much closer. The optics are high quality giving you sharp pictures. I've used off brand optics before on film slr's and they just don't compare to Canon's quality. They are worth the extra cost. The price I paid with Amazon was a bargain compared to brick and mortar shops I checked.
Summary: Not an ideal situation as the lens restricks the camera minimum zoom about 1/3. So minimum zoom is no longer the minimum. But it takes great indoor shots without a flash so I expect better things when outside. Also note that a polarizer that fit the adapter does not fit this lens. So you either use the adapter with the polarizer or the adapter and this zoom but not both.