I used it and for me it was the best prep material for orgo. It may be an overkill but it's better to be over prepared then under, but to be honest it's not that bad, if you have time, do it.
I think it's a great resource. Is destroyer better? Probably, but once you've gone through destroyer a couple of times, it starts to lose its effectiveness. You want to do as many practice problems as possible and the ACS guide is a good source.