I feel like researching on your own helps a lot too. Opinons are useful, but only if you agree with them and the match pretty good to what you think yourself. I mean, you can use them to back your own claims up too. But I think having your own grounding in Socionics helps too.

"Professional" typings can narrow things down if you really are stuck, but there's no point going into it completely blind and taking what X person said as gospel because you spent money on it. You need to think critically for yourself as well. Not saying that they can't help (they can help) but what I am saying is that they are a part of the analysis, not the whole. You know?

Sometimes it's worth investing in, other times not. You need to know what you're getting yourself into. Weigh out the pros and cons and see if it will work for you. It's not a complete means to an end, but it's a tool than can help.