Used this a few times and not disappointed. First attempt went ok, except I didn't make sure it was in straight. Second attempt on make perfect circles every time. Seems to work well with average to large size pinapple with little wastage. Try to get one that sits reasonably flat which makes it easier to put in straight. Apart from that it is plain sailing. It cuts perfect rings, well one continuous spring really which you then cut down one side with a knife to get the perfect ring. As well as the look the thickness is also perfect, I find if I cut with a knife the slices are always much too big, these are just right. There is still a little mess but not nearly enough as when you cut by with a knife, it is possible I've not quite worked out how deep to go meaning I'm piercing the bottom and letting some juice escape. There is a decent amount of juice left in the bottom which can be poured into a small glass and tastes delicious. The leftover shell works great for presentation of a fruit salad at a dinner party. I suspect you could also cut the pineapple in half (rather than cut the top off) and core one half and put the other in the firdge for later, I've never tried this as I love pineapple. Considering I love eating pineapple (2-3 per month) I wish I'd got this years ago. If you search YouTube for "Stainless Steel Pineapple Corer" there's a great video which shows exactly what to do, it really is as simple as that.
Edit: Now owned this for a while and would re-iterate how great this is. I now eat 1 pineapple a week because it is so easy to cut. The pineapple without a doubt tastes better when it is cut to the perfect thickness.