I'd like to try one out but don't want to be totally dedicated to it if I don't like it. I have a 1020 now on AT&T and would like to keep both but switch the SIM cards. Any tips on where I can get a good used one for a reasonable price?
Little problem with your Sim swapping scenario. First off, the 1520 and 1020 have different Sims. One is a nano and the other a micro. The 1520 has the nano which is just like what the iPhone 5s and Moto X use. This means ATT would have to get you a Sim for the 1520, making the 1020 Sim useless.
Then you need to buy an adapter on Amazon so that the nano Sim works in a micro Sim slot. You can get one for about $5.
Gazelles eBay store is a great place to buy nice used phones...I've purchased from them many times and as said about the sim differance, just purchase a cheap sim adapter from eBay also, they are really cheap.