This is an interesting question. I would say that I got into typology because I'm a seeker... I'm always looking to better understand myself and those around me. I basically use MBTI as a tool to aid in understanding what makes people tick. It can help me understand why someone might react a certain way, feel a certain way, think a certain thing, and I think that helps me understand where that person is coming from and can often help their perspective make sense to me, or at least I can see how it would make sense to them, so this allows me to be less judgmental and dismissive of people who think differently from me. It's also helped me really become okay with who I am and my preferences-- I spent a lot of my life trying to "become" an extrovert, and it really never worked for me. MBTI helped me realize that we all have something to contribute-- different perspectives, ways at looking at things, etc-- and that being an introvert is no worse (or better) than being an extrovert. Likewise with all the other functions. Now I don't waste energy trying to be an extrovert, because that's never going to happen. Instead, I focus on making sure I allow myself to be an introvert, and make sure my needs as such are being met: I try not to overextend myself socially, and plan in "I time"; I try to identify what I need, as an introvert, to deal with things that might come more naturally for an extrovert, but which I still have to do; I am honest with people when I turn down social invitations because I need alone time or the particular activity, which is meant to be fun, would not be fun for me-- instead of making up and excuse, I do my best to just say "I need some alone time" or "I'd love to hang out with you, but this party isn't my thing and I'd rather spend time with you in a setting where we can really talk."
How has my opinion changed... I'm not sure. I've definitely learned a lot more about typology and how the different functions interact with each other. The more I learn, though, the more I think MBTI needs to be used as a lens with which to understand people, not a system of classification.