Let me preface this saying I have not pretenses at being an expert at VA regs..they can be mind-bogglingly complex. But here goes. ACF is the Army College Fund. Not everyone is eliglible for this. It is an enlistment bonus that is paid to specific MOS's (or at least it was when I enlisted in '97.) Generally, it is used at an incentive for people to go into the more undesireable MOS's, like Infantry. This is why I got $40K. I could have also chosen a cash bonus of $12K. I had definite plans to go back to school, so I took the ACF. I enlisted 11Bravo for 4 years, so I got the max ACF. (You earn it, trust me!) For MOS's that are in high demand (like MP or computer stuff), they did'nt give the ACF...they did'nt need any additional motivation to get people to enlist for that job. Remember, this is my experience from 1997, so it may have changed.
In contrast, everybody who joins is eligible for the Montgomery GI Bill. You contribute $1200, and after some period of time, you get so much a month while going to school. IF you enlisted for the ACF bonus, then that amount is added on top of the GI Bill. This is why I get $1450. I think just the GI Bill alone is like 800 a month, maybe more.
The guy who said it is stupid not to get the GI Bill is right...it's a relatively small investment that has a great payoff when you go to school. You will NOT be sorry you gave up $1200 initially.
Try this website for more info...they do a good job of explaining it. <a href="http://www.gibill.com" target="_blank">GI Bill web page</a>