Mine are almost 5.5 years apart. I wanted them close together (I thought one year apart would be good, until I realized how hard it would be to have an infant and one year old at the same time!!!) but it ended up not working that way (had to trade husbands...).
So, the wonderful part was that I had my DS right after my DD began kindergarten. She was busy with school and I had lots of time with DS and I did not have to worry about her being jeaulous. At five years apart, she could be a big help with entertaining and diaper changing. They can play wonderfully together with their own made up games, and they rarely fight over the same toys, because they have different interests.
I guess the drawback is that they don't always play together, but maybe all kids are like that??? I still need to arrange play dates and their own activities, but I think that is to be expected, since even kids born close together can have very different interests.
Good luck!