On the topic of the 'like' buttons, personally I 'like' these. In the beginners' section in particular, a question will often receive multiple and varying responses. In these instances I tend to see the like button as a way of putting my support or agreement on a particular post without having to basically repeat the same thing in my own post. I see it as a 'vote' for the suggestion/idea given in the post, and I think it's useful as a beginner to see the amount of support behind a piece of advice. Of course the 'like' buttons are also used to simply like content such as a photo, or someone's good news, but I don't think their role as an expression of opinion on ideas/suggestions should be overlooked.
Personally I would appreciate a dislike button. Whilst the forum is generally fairly good natured there are times that I find the attitude of someone's post unpleasant, condescending or bullying. I haven't yet found a situation in which I would report a post, as for me this would have to be a clearly abusive post (perhaps others have a lower threshold for wanting to report a post), and also an instance in which I didn't think I would get jumped on by a lot of the regulars who would likely be in support of their friend/veteran member.
A dislike button would allow me share my disappointment with a post. I am sure there will be those that would say I should add my own post calling out the behaviour, but for me that's simply adding more negativity and seems to be lowering me to their standards of behaviour. I agree with Pargyle's 'if you can't say something nice, don't say anything', but I interpret it differently in this situation. The point is that I don't want to say anything that isn't nice (I don't want to post anything negative, and get drawn into that downward spiral that we often see), but I do want to show that I don't think what was posted was nice or necessary. I believe a dislike button would give forum members a less confrontational way to show their opinion of an unpleasant post.