I just finished reading all 27 pages of this thread and some of it is rather amusing!
Before I get into what I wish someone had told me I must say it's rather amusing reading a post that says something along the lines of 'I wish someone had told me that omnis would try to establish veggie cred' and then later reading a post from an omni trying to establish veggie cred for being a vegetarian 'every other day'. NOT to knock those who used to be, and would still be, veggies if not for certain health issues. The irony just kinda makes me giggle.
I only have one thing I wish someone had told me: how satisfied I'd be with my eating experience! For almost 4 years (with a 6 month instance in between somewhere when I ate hamburgers that I don't count in the total time) I ate anything but 'land meat' (i.e. only poultry and seafood-water and sky meat) and eventually I started just feeling bored with eating in general (which was really really bad) until I cooked some recipes from the copy of 'Vegan With a Vengeance' I got for my vegetarian friend. Immediately my interest in food was rekindled and now not only am I a better cook, but a better eater too!