A friend has a Leopard motor in his Hyper7 and Revo. I have to say that do perform very good. Temps are similar and power seems to be on par with Castle. Where I see a problem with the Leopard motors is what are you going to do if your motor craps it self? You will just have to buy another. What are you going to do if there is something wrong with the motor right from the box? You might be luck and the seller you bought it from will look after you but every chance they will tell you to go away.
If you buy Castle you get more than good quality product. You get support as well. Look at what the guys from Castle (and even the man him self Patrick) are doing here. Answering questions, offering advice and really looking after their brand and company image. That goes a long way in my books.

Still I have to confess. I do have a few Hobbywing ESC but they were cheap for my cheap cars and I know that they will go straight into the bin if anything goes wrong with them. My Castle gear is in my better cars and I know if anything happens to it Castle will be there to get me going again. If I was offered a Leopard motor for $30 I might take it but they go for around the $100 mark. I am not a gambling man and that isn't chump change to me.

As far as cloning goes I doubt that they didn't go over the Castle motor with a magnifying glass and a micron gauge. They are just way too similar to believe other ways.