There is a 4 yr age gap between #2 and #3, and I have to say, it was SOO much easier than the transition with my two that are 26 months apart. The older children adored the baby, and the age difference seemed to eliminate any sibling rivalry issues. My 4 yr old was able to help with all kinds of things, which made her feel more involved with the baby from the start. She was verbal enough to make her feelings known, and able to play by herself for periods of time without needing my direct supervision.
#3 is 4 now (dd is 8, ds1 is the oldest) and has never really known anything in his life but love and kindness -- no siblings take his toys, or pushed him down when he was learning to talk, no one gets mad at him for invading their space, etc. It's really, imo, an ideal age spread.
I did worry that with that age difference, the older kids might not be as close to him as I would like, but that hasn't been the case at all. From the day he was born, they have loved him and taught him, guided him, and protected him. He, in turn, thinks they are the most incredible beings on the planet.
Not sure if you had more specific questions, but I found it, overall, to be a really smooth, painless transition, and I really like that age difference.
Joy, mama to Aquaboy (10), Goldilocks (8), Squidge (4)