Arrythmia below is entirely correct. Princess Bubblegum is often classified as 'Lawful Neutral' or 'True Neutral' because she isn't clearly good or evil. I'd say in general, PB is more good than evil, as seen by the ending of 'The Cooler', where she disables her spy cameras. However, she does dabble in some shady activities, particularly in her scientific ethics.
Speaking of the cameras, there is political commentary here. Many times now, in episodes such as 'Lemonhope', parallels have been drawn between the United States and the Candy Kingdom, and the cameras reference the NSA's suspicious activity. I'd even go so far as to draw a parallel between the Fire Kingdom and Russia. In my view, Cinnamon Bun is similar to Edward Snowden. CB was close to PB and was way in on her secrets, in some ways anyway, and like Mr. Snowden, he went from being PB's close friend to suddenly jumping to Flame Princess' side. I digress... back to PB.
PB means well, she really just wants to protect her people. I am repeating Arrythmia's commentary, but PB really is just being a princess. In 'Pajama Wars', she is temporarily freed from governing a country... We see her become an ordinary teenager, one who might be cramming for exams or browsing reddit or getting drunk recreationally. Inside, she's really just a girl, who has way too many responsibilities thrust upon her.
I used to furiously dislike PB during much of seasons 4-5 because of her treatment of Finn, her candy subjects, and other characters (i.e Braco in 'The Suitor'). When she is in her professional, scientific, diplomatic mode, she is playing the world like a game of Civilization Five. Finn is just an easily manipulable annoyance to her at this time. More recently, however, especially after she let's go in 'Pajama Wars' and agrees to try and be less of a computer and more of a person, I find her tolerable.
PB is a wonderfully deep character and a feminist symbol as well. One could write many wall of text on PB alone, just analyzing her character, actions, relationships and plot mechanics. The depth of PB reflects the depth of all of Adventure Time, and is the reason I love AT so much.
tl;dr PB is cool