I'm still trying to work out when an Annual Pass becomes a good deal, but I think if I do end up delaying my first trip so that I take two trips in one year, then I will get one.

Theres a ton of discounts available to Annual Pass holders, and some of them are pretty good:

Disney Annual passholder discounts, Annual Passholder specials at Disney

Now just to find the willpower to put off long enough to make it worth getting one!