After much Testing of various Server files, 4/5X Exp is about right, you level fast enough but not too fast that you will reach level 50 in a few days of playing.
WhT i feel is important is an Economy - so things do not have to be rare but harder to find and NOT on the shops - then people start using the Commisioner merchant as well. No matter what Exp, Drops, Mobs etc you shove in the game, you will not please everybody. Make the server how YOU want it to be and they will come BUT you need Stability and No Corruption and both of these Johny was a problem on all the servers you ran.