Air National Guard for 5 years, separated at the end of 2012. Miss it constantly, and perpetually reconsidering the decision. Only problem is that I would have to crosstrain into a different field, as there are no Air Guard units nearby with my AFSC.
I've got a few more years that I can hold onto that option though.
Honestly, I hate being a civilian. I hate almost everything about it. Leaving active duty was one of the worst mistakes I've made in my entire life, and leaving the guard was the second worst. I only left out of necessity in the foolish pursuit of a civilian career.