It seems like, if these are legal, it would be rational to use them, unless they introduce new biases that are counterproductive, or you wish to develop your probability and card counting skills...

Of course, and indeed essentially all serious online poker players do use poker analytics suites. (They are legal. The point where assistant programs become disallowed by the sites is, essentially, if they start doing the mouse-clicking for you.)

EDIT: It turns out that the above description of exactly where the line between allowed and forbidden is drawn is mistaken. See this FAQ for a comprehensive presentation for how e.g. the biggest poker site lays down the rules on this matter (may vary a bit between sites).