I use Lee dies exclusively in my Dillon 550B with one exception. The dies work just fine and the price is righht. Make sure to buy carbide pistol dies.
I always use a Lee factory taper die in the final position....using the bullet seating/taper die only to seat the bullet. I had previously had some feeding problems which led me to use the taper die...no more feeding problems.
The exception is for the .223. I had big time chambering problems with my .223 reloads. I found out the problem was the dies and a fairly tight chamber. Some folks on one of the chat rooms put me on to small base dies for the .223 and I got a set of RCBS....no more problems.
Hope this helps, Mikey