I'm all for it.
Someone mentioned only users with x amount of posts could rep and be repped, I think you should do it this way.
Don't forget, there is usually a limited amount of rep you can give out daily, like 5 people or so, so you will use them wisely, if at all. You also cannot rep the same person more than once in a certain period of time. I'm sure both of these options you can change the amount of time for each, so you could give like 24 or 48 hour limit on how many times you can rep the same user.
If you keep a relatively close eye on people and the rep system from
the start, it will be unlikely that people will have monster rep points which will put a regular user way down into the red if he feels like an asshole.
Besides, I ahve a feeling
most people on this board who will have the higher rep, will have
earned it, which implies that they will more than likely not abuse the sysem to there is no need to worry about that.
I like reputation systems, they are fun, can provide constructive criticism, and offer motivation for the losers who feel good from having high rep poitns (

) to actually contribute to the board in a good and helpful way.
Again, I'm all for this. If you're skeptical, I suggest you make up a backup of the forum, and install the mod anyway. Try it out for a month or two, and if it's too much of a hassle or you think it is affecting the community in a negative way, scrap it.
<<banned from SRF for rules violations. -SG>>