We have about 16 months between our boys. it was really, really hard in the beginning, much more than I anticipated and I thought I'd made a huge mistake but now they're becoming best friends and it's absolutely adorable. Imran is at an age where he gets a bit of seperation anxiety and he often has a bit of a sook when Yasin leaves but when he comes back he's all giggles. They already play goofy games with each other and have 'conversations' . So.... even though the first few months were really tough I don't regret it now I see how close they are.
That's my own experience but everyone is differant and i can see that there would also be advantages to a larger gap.
The way I see it Imran will get his one on one time with us when Yasin starts school so he won't miss out so mauch as have a differant experience.