I was ready when my son was about 3. I actually had my second when he was 7 1/2! Sometimes things just don't work out like you think they would!
Somethings were easier having a big age gap. He was old enough to understand that sometimes the baby just needed more attention. Somethings are harder. Ever try going to a water park with one that is raring to go on the huge water slides and one that is just barely walking? Hard to balance!
I think the key is making sure you are making the decision, not others. I know that as soon as I had my son i started hearing from others that it was time to have another. Not really from family or close friends, but from strangers! Sheesh! I also went back and forth about not wanting to share the attention I was giving my son, so that was always the reason I gave for not having another. (Not that I really needed to explain to ANYONE mind you!)
I think that in an ideal world I would have had my children closer in age. I was about 2 1/2 years older than my brother and I do feel sad at times that my children will not have that bond. They will have a bond I know, but not the same kind that I had with my brother.
You WILL be able to love them both SO much. Love just multiplies! And it will all be just as special the second time around. Also remember, that when you do decide to get pregnant, your son will be almost a year older by the time you have the other baby.
Do what feels right for your family. Don't have a baby sooner because others are pressuring you. It is YOUR family. YOU make the final decision. Whatever you decide, it will turn out to be the perfect decision :)