I have one for Canon and using a fisheye is harder than it looks. but at this price, if it's well worth experimenting with.
Nah, don't worry. The people will always look like that with a fisheye, no matter what you do.
If you mean that it's hard to get a worthwhile shot, that's true. You really gotta get up close and personal to get any subject detail (vs just a wide-angle distorted shot of the world.) IMHO, you can do fun things with kids that don't look too wacko, particularly if you undistort them. Adults, however, probably wouldn't appreciate the way they look.
Keep in mind this:
On APS-C cameras, the pictures will fill the entire frame or screen. On full frame cameras, the lens will produce pictures with a semi-circular image and close images will appear proportionately large for a dramatic effect.
So it's a full-image fisheye for most users (on APS-C) and a circular fisheye for FF users. Tempted to get one since I have both formats...hmmm..