Any question answered...

Ha, Mark and I are constantly cross-posting and coming up with very different pieces of advice. :)

But I can understand you wanting to avoid those words (life-changing/altering) as they're a bit of a cliche. Just don't use the wrong word! (which, obviously, you're making the effort not to).

I suppose at the end of the day there may be rules for such applications that mattty may be able to find somewhere. I think 'life-changing' is fine, but I don't know whether it may be something that the people reading such applications are heartily sick of.

I suspect what's hard to capture is a sense of having improved through the process. The technical term for that is really 'edifying'/'edification', but that sounds even more pretentious. :)