Are these cheapo screw-in fisheyes any good? Will there be loss of image quality? Something like this? http://cgi.ebay.com/ws/eBayISAPI.dll...520654735&rd=1
The prices on the fixed fisheye lenses are out of my ball park, but I have wanted to try one of these things. If they suck though, I won't waste my money. Please let me know your thoughts. Thanks.

Dave