Cool! I tried something like this, it classified blog posts into 100 different moods... it had ~8% accuracy (It also classified as positive or negative, but I don't remember the accuracy, I'll have to dig it up at some point...). Good luck with it.
Do you remember what was it? I will be really curious to have a look. Thanks.
It was accurate around 56% of the time classifying as positive, negative, or neutral. I used a naive Bayesian classifier and guessed the highest rather than showing the percent positive.