Special Forces is what got me into the sport; from the first day I played there I knew I'd be hooked for life. Since then I make it a point to come back at least a few times a summer (in spite of the almost two hour drive).
Maybe it's just nostalgia, but no outdoor field has compared up to this point. SF staff is very, very friendly, the fields are HUGE and well laid out, and the bunkers have a great sense of authenticity. Everything, from the truck ride at the beginning, to the staging area, to the game organization just reeks of professionalism. The guys who work at SF clearly love paintball and really want to spread the love.
In the three years I've played at SF, I haven't had a single bad experience. Well, aside from the heat-seeking, bat-sized vampiric mosquito population that lives out in the woods. But that's just Minnesota.