I got a Calypso Jr. ZDP. I think I liked it; after I used it for the first time, I immediately ordered another. If anybody has both, my question is, how much practical difference is there between the Calypso Jr. and the Calypso 3?
I have both. I can tell you that in my house, the Caly Jr is a drawer queen and the Caly 3 is a user. There is nothing wrong with the Caly Jr, but I don't like featherweight knives. I bought it just to see what all the talk was about. I was pretty sure from the description that I'd not be using it much. Mine is a fine cutter, but just doesn't suit me for carry.
Now then, let's talk about the Caly 3. She was a surprise. I walked into Ruff's Saddle Shop in Umatilla, FL to buy another ZDP D4 and saw this thing sitting in the case. The man let me hold her and I couldn't give her back... so he made me give him some money

. That's OK... what's money when you're holding a Caly 3?
Practically speaking, the Caly 3 is a very different knife to me than the Caly Jr. They share a common history and some characteristics like a back lock and a flat ground blade, but the liners and scales of the Caly 3 give an entirely different feel to this knife. I always feel like I have more control over a knife with a thicker handle and some weight to it.
The blade also seems thicker and has enough of a different shape to be much more attractive to me than the Caly Jr's blade. It think that it will be a sturdier blade because of the added thickness.
I think of the Caly 3 as the Caly Jr all grown up

. If you like featherweight knives, the Caly 3 may not be your cup of tea. It's very comfortable in a pocket, but you'll know it's there. OTOH, if you want a tough little knife that has some substance to it and can play over its head with the big boys on occasion, then the Caly 3 will be just what your lookin' for.