I just bought the 2014 RI EL Z2K from the SBF store in early August. I received it on a gameday. 1st game, it didn't feel very good. This was my first 2-piece bat so I was getting used to it. I had an hour off and a buddy of mine and I hit with it before our 2nd game and could tell a difference after we were done, maybe it was me getting used to the 2-piece, maybe it was opening up a bit. After that night, I probably had 100 hits on it.
Fast forward to Monday, the bat probably has 400-500 hits. I subbed for a team that night and all but one guy used it because they only had two bats. It definitely is getting better with every swing but still has that unforgettable LS ping. I had many of the guys tell me that they really liked it.
For the price that is on SFBs, it is a GREAT DEAL for a GREAT BAT.
P.S. I just bought a used 2015 USSSA EL from a board bro and really like it too. I don't think you can really go wrong with either the 2014/2015 Z2K.