To be quite honest, I can't say I like the new rating system either. I'm not particularly fond of 'like' buttons of any kind, but this new system just turns the forum into a popularity contest.
I also disagree with a point made by Tom and Bram - that the new system improves contributions and activity. The thing is: rating someone's post is not an actual contribution. It takes zero effort and there is basically also zero benefit from it.
The worst part about it is the anonymity. If someone's got an opinion, they should come out and say it. If you can't even stand with your name behind your opinion - why should I respect it?
And when 'likes' and dislikes are merely stacked up and counted, the individuals behind them lose meaning. This might not exactly be in the spirit of democracy, but in my opinion, not all forum members are created equal. To me, a 'like' from reasonable people like Bram or Hampus (most of the time, anyway :-p) means a lot more than, say, from the random Vettel-hater crowd who'll just 'like' anything sufficiently negative about him. The anonymity takes some of that away. It also kind of goes against one of the fundamental RD principles, encouraging a mature conduct by posting and racing with real life names (which also has been undermined on other occasions, but that's a different story).
Additionally, the 'like' system wasn't used particularly well until now. I admit it's been a while since I've read through the forum rules but I remember there being something about how you should 'like' posts because they are useful and constructive and not because you find them funny or because you simply agree with them. My observation is that most likes are used for funny posts or pictures (which, coincidentally have been posted three times before), followed by the trench-warfare of the Hamilton vs. Vettel vs. Alonso fans (each liking the posts of their comrades). Somehow I don't really see the new system being used any better.
Overall, I just think the like system was bad enough as it is, and this won't improve it.
If you want constructive criticism on how to improve on the new system: keep it in place but take away the anonymity. Perhaps it should display the names of the people who did the like/dislike/rainbow/whatever on mouseover of the respective symbol, or something like that.
Oh, and ponies rule.