I spent six years in the Marine reserves, I am now active Army.
I hated the reserves. It was hard to turn the "Grunt" in me off and on. I lived far from all other guys in my unit, so I didn't get much comradre, these were just guys I just saw once a month. It seemed that reserve weekends always fell on the same weekend that wedding/concert/party/seminar always fell on. I busted ass 40-60 hours a week, and my time off was spent playing GI Joe. I just about broke even, covering gas and food vs the money I made at reserves (not to mention the loss of overtime).
And I do mean playing. These guys never saw the real service, so they just had an idea of what it was like. Maybe that was just my unit, but leadership was lacking. There is little time to train, you spend as much time prepping and doing admin as you do training, and by the time it gets going well, it is time to pull it in. And preperation for war... it was the quality of men, not the quality of training that kept us alive.
Also, in this day and age, reserve and guard units are deploying as readily as active units.
Well there are good things about being in the reserves, I find active a much richer and rewarding experience. I wish I would have done this initially, and maybe reserves later in my career.