I'm not vegetarian but I don't think I eat a lot of meat. My main contribution though was on the whole cheese thing which seems to be most people on here's reason for not considering veganism.
It turns out we have a baby who is intolerant to dairy (apparently it's common and they usually grow out of it). Anyway, because my wife is breast feeding she can't eat dairy either or the proteins will pass through to the baby. As a result we haven't bothered buying cheese for a few months now as I couldn't justify sitting and eating a load of cheese by myself (i'd probably feel a little bad about it too :P).
Despite loving cheese, it turns out if you don't eat it for a while you don't really miss it. In fact, I'd say the thought of eating a lump of Bree even sounds a bit overindulgent having not had cheese for a while, it seems a bit like eating a dessert spoon of butter.