It has trouble with negation outside the relevant clause. So it is not fooled by e.g. "I don't hate it" vs. "I don't like it", but the first of the following two sentences is rated more negative than the second:

I don't seem to hate it.

I don't seem to like it.

Edit: In fact it can even be fooled just by increasing the linear distance between a positive term and negation. The following is rated +0.6!

I don't in any way shape or form like it.