In my opinion, Rep represents ones ability to contribute to the community through your posting of quality maps, links to mapping sites and posts of an informative/constructive nature. Something that makes me say "Wow" for some reason or another.

Likes for me are for posts that say or illustrate something that I agree with. Be it map, post or link. It has happened that I have done both for the same post if it met both criteria.

Rating threads is a statement of how useful I have found the info in that thread, and how much I would recommend that people read it. I must confess that I have not been rating nearly as many threads as I should, but I know I keep on forgetting that that option is available because it is kinda hidden.

I think that all three are relevant,and separate, but that they should all be placed in the same area so people are more aware of the options.