Have to say PicLens is cool!
It is especially great helper when you do images search of Google. I can navigate along the pictures like they are in an album. No need to click Next button because PicLens already do it for me.
Yes, although PicLens annouces that Yahoo! supports it, I find that Yahoo! Image Search does not do things well. To be more specific, it seems that Yahoo!'s Media RSS source does not have the automatic-go-to-next-page feature like Google's. So you can only view pictures in the current page. Very very inconvenient!
BTW, once I have reported to PicLens that I cannot view one of my Picasa album in it. Then I suddenly realize the cause is that I navigate to a UK version of Picasa where Media RSS is not correctly implemented. I do not know whether now the issue has been fixed.
And now PicLens provides Firefox and Safari a big advantage over IE because it does not support IE right now. So if you want to try PicLens, please install Firefox or Safari (both can be installed on Mac OS X and Windows).