I'm not sure, in some ways, that I gave the matter a great deal of though: it seems so much that the most the important steps I've taken in life have kind of occurred unexpectedly, or at any rate, without explicit or direct or extensive forewarning.
Biggest difference? I thought I'd be married, probably by now (I'm 33), but, well, anyway, that hasn't happened, yet. I suppose the career (could one even say vocation? perhaps, sort of) isn't exactly what I had in mind when I was younger, but it is kind of related to earlier dreams, hopes and plans. My other plans to escape living in a big city also came to fruition (more recently), again, not quite as I had previously anticipated they might, but all in all in a better way.
In any case, I've still 7 years left of my thirties. Hopefully they will be every bit as much a time of development and growth as my 20s were (with the added bonus of experience and hopefully having learned from past mistakes)