I recently bought these tile nippers in a bid to get into making some mosaics for my garden from donated tile. They were the first item that came up in a search for tile nippers and they had decent reviews, so I purchased them on the strength of that.
I had not used tile nippers before, and perhaps I did not choose the appropriate type for the tile I had--somewhat thicker ceramic tile. However there is no indication as to what these can easily handle. Well, having practiced with them I can tell you that as a twentysomething woman with pretty good hand strength, I can nip the corners off old wall tiles if I use two hands and press with all my might, but I certainly can't nip with one hand while keeping hold of the tile with the other hand. The result of this is that with each successful break, the smaller bit goes flying off to ricochet around the room--not very efficient or safe! Nor can I break a tile in the center or anywhere other than at the edge. The leverage is just not great enough, and the process of nipping the corners takes so much force that there is no room for any dexterity to cut out a particular design, say a petal for a flower or anything like that, without spending all day at it. Given the lousy results, you might as well use a hammer and/or the more traditional hardie (a kind of pointed anvil for breaking tiles) and just give up on forming anything but shards from your tile (which is a legitimate material for mosaics, anyway). I did try nipping a thinner fired clay bowl and I managed to do a bit better there, but still there is very little control possible.
I have looked at several books and websites and the conclusion I must come to is that these nippers are probably reasonable for the very thin or "soft" types of tile (4mm), but for the 10mm thicknesses and other, harder materials there are much better tools! Before spending money on these, consider looking into nippers with sharp metal wheels on the end (glass tile cutters), porcelain nippers, or stone nippers. I'm led to understand that each is a separate type made for progressively harder surfaces, and they ought to do the job.
In any case, these nippers being reviewed here will not allow you any kind of finesse when cutting, and that is IF you can get them through the tile at all--if you are an unpracticed hand, best to look elsewhere.