I used share for a while (for about a couple of months). The reason was the incredible speed it achieves, many times quicker than a direct download, maybe the ISP are throttling down download websites in the place I live, but they haven't throttled share yet.
The main problem you will find with share are:
-- Most of the content is only indexed in Japanese, so you end up cutting and pasting text you do not understand and try to get something by trial and error.
-- But you are not sure what are you downloading because share likes to start downloading at the middle of the file and it is unable to recover any partial file to check its contents (as many torrent programs do).
-- When you test the full download, turns out to be real shit (I consider myself very open minded but I think some Japanese have to be very screwed sexually speaking). When I say SHIT is real SHIT that keeps rumbling in your brain for hours.
-- After a couple of such incidents, I deleted share from my hard drive, and I only download from places like rapidshare and only when I can have a look at the thumbnails
It is a pity share does not have more content indexed in English.
Cheers