Desert Fox is my field of choice in the Tucson area. I've only played rec-ball there, and it is a lot of fun. The field is huge, and I like the strategy that can be involved in attacking/defending from another team with such a big field. There are trenches, broken down cars, pallets, boxes, two tire bunkers facing each other, and even an airline fusilage. Some of the refs there can be inexperienced, and will often park their golfcarts in the middle of a firefight, or make a player stand up for a paintcheck, even when doing so will expose them to enemy fire. The field is so big that sometimes the refs aren't around to give judgement when it is needed. The inexperienced refs come and go. There are 2 refs there that are very good, and regulars. They're cool to talk w/ and what-not. The other problem with the field is that you are required to use field paint, which is purple shell/purple fill Kick'N rec Paint, or Kick'N Mettallix. And the field paint is pretty expensive. On the up-side, the field fee carries over for the weekend, so u could go on Saturday, and come back Sunday w/out paying a fee.
Overall, I really like this field, and my only major complaint is about the field-only paintballs. The occasional inept refs don't really pop up all that often.