there are a few good reasons to use boost.
1) I've heard, not sure if it's true, that 1 boost is about the equivalent hate of 1/3 of a provoke. I know I get quite a bit if I use it in an exp party too much. Just in case you ever for some really really odd reason have to pull hate, you could try spamming boost.
2) It does improve damage. but at level 5, it's not going to be terribly noticable. at 56 I can boost up to about 800 attack. trust me, that's noticable, and not advisable.
3) Berserk + Boost + Weapon Skill = Beat down, throw in focus for raging fists or any weapon skill where you hit more than once. I try to space them out though, so I don't pull too much hate. throw out berserk and focus at about 60-75% TP then boost right before you use your weapon skill.
4 Boosts + mnd gear + Chi blast = insane damage.
