I don't know what cruise line you are on but with RCCL, yes they did just push the beds together but there was a board laying horizontally between the two beds and this did stop the two beds from sliding away from each other. With queen sheets, neither my dh or myself noticed and found our bedding to be very comfortable.
They use queen sized sheets. We've never had a problem with this. It's worked out just fine. You get more room if you have the beds put together. What we liked on Carnival Fascination was that one control near the bed took care of the lights, the tv, etc. and we didn't even have to get up!