We have a 3yr gap and it was great. DS was old enough to really understand when I needed to look after DD and entertain himself for brief periods (which was lucky since she had bad reflux and hardly slept!). He was at preschool so I could nap some days, and he's such a loving big brother. They are still close enough to play together and they are good mates and have a lot of fun.
I would want the same or more if we had another one. It's worked well for us. Also I get very sick when I'm pregnant so I'd not consider it again until DD is at preschool and a lot more independent.