I kind of doubt these tests but the little positivity they offer is that they make you wonder about yourself, ponder on your behaviour, your reasoning and motivations. The negative side is that some people become elitists, stereotype others and might not be interested in someone simply because of their type. All of this can probably be summed up by saying "I can't get along with an ISFJ, they are too traditional and won't understand my superior intuitive thinking."
Also, I think my level of scepticism depends on the approach, I tend to distrust ones that over-rely on black and white letter dichotomies and/or so called "cognitive functions" more. On a side note, I've also taken a Big 5 test, which was interesting but doesn't tell me anything I don't already know. I guess it's useful though for people who have trouble observing themselves.
So anyway, I got INFP-T from 16personalites, which claims to have their own MBTI theory adjusted to resemble the Big 5 (
here's their explanation). At least I give them some level of credit for updating and presenting percentages rather than dichotomies or questionable "cognitive functions". It's some good fun, especially when I made my husband take it, he predicted he would get an evil result (knew nothing of MBTI at the time) and he was correct (INTJ known as the "evil mastermind" to some). I was just laughing while he was making and evil face.
And although he has recognised some accuracy to the description, he also says it's too simple to think of people as 16 types.
It takes a big level of honesty and clarity as well, the results can be influenced by your bias. For example, I got INTP in my teens because of my "rational" phase... Which wasn't at all, it was clearly fuelled by deeply repressed angry emotions when looking back. So take this with a salt shaker, cause you'll need more than a grain!