I think it's helpful to define, as best as possible, what is meant by "bitter." Personally, I don't believe that being a little sad or angry at the JW system is wrong or unhealthy as long as that anger and sadness is not out of control or beyond what one should feel. Bitter, to me, would be seeing the totality of our JW experience as being totally bad and/or useless. It means being overly preoccupied with being an "anti-Witness" in time and energy. It means blaming the JWs -- including the GB -- for everything wrong or inadequate about the JW system without seeing the possible underlying good intentions they have. (I know that is difficult for some here. Personally, I believe the vast majority of JWs, including the "higher up's" are operating out of a sense of what they, mistakenly, feel is right)
In short, "bitter" in my book is being overly angry/sad about the JWs without seeing the good and the underlying reasons as to why the organization exists as it does. (And this touches on human nature which is so incredibly far from ideal). It's essential, in my opinion, to think philosophically and magnanimously about the JWs and our past and present relation to them. Only then can we have a measure of equanimity and peace.
Overall, I'm not bitter -- although I do have my moments!
As for "better" I would say that it depends on the sphere of life we are talking about. I feel far, far more confident about myself and my life choices since leaving the JWs. I feel a tremendous amount of intellectual, emotional and situational freedom since leaving. Those areas are far better. On the other hand, I do miss the strong sense of community and unity of purpose. (These were carried to extremes in the JWs, of course). Humans evolved to be part of a community of between 20 and 100 people (think of a proto-hominid tribe living on the African savannah) and our modern world of hyperindividualism seems to be in conflict with this very human need. So, in that area of life, things are not better for me.
On the whole, though, I feel much better being a former JW than when I was inside the organization.
B.