PMR has a lot of functions pertaining to the necessities of a smart phone (battery mods, software and apps, CPU modifications etc) the adrenaline booster is basically just a shot for the system to wake up. It has init.d tweaks for the early riser who has a lot of startup apps like messengers, down loaders, twitter/Facebook/xanga whatever. It also has a swappiness tweak that can let you use some of your internal or external memory as backup ROM for super memory hogging games. My favorite tweaks are your basic build prop tweaks, all the basics like hardware acceleration, scroll speed, 1x/2g/evdo/4g buffer and a bevvy of other mods.
Zimm is right though, it does drain battery. That only happens when you have doubles and triples of the same tweak in your build.prop though.
So for everyone's sake, the adrenaline shot is only meant as the first stop for someone using a new ROM and is to lazy to manually add in the lines. (Like myself ;D)