I haven't been playing that long as a newbie but I did make some observations out at the Modesto field. First the staff was very freindly and helpful. While the refs have been chastised in previous posts, they were very nice and helpful to us. I would say in the speedball field they were very good at ref'ing but in the bigger field there just wasn't enough of them to really do a good job. You almost have to be on the honor code if you get hit. The nice thing is that most people do go out if they get hit. Entry fee and rentals is cheap, and paint was decent.
I'd definately go again when I'm in the area. Too far for me to drive out there just for a couple hours, but I would for the whole day. Bunkers are good and if games were longer on the big field it might be more interesting for strategy and teamwork.
Overall rating is 9/10 and I will definately go back, but with my own gun and not a rental.