A.,
I sense the reason for the devastation in your friend's case is that she had twins, which is entirely different than having one baby.
I belong to the Centerville chapter of MOMS Club (an international organization for stay-at-home mothers). You may want to look into this yourself. Great network of moms and a great opportunity to socialize your kids, too. Anyway, most of the moms with 2 children had baby #2 when the first was 2 or 3. It is a nice spread.
My two are great at 2 yrs apart. I can, however, see the benefit of having them 3 yrs apart because you have a shot at having one potty trained and you likely have one talking at 3 also. Neither was the case with my first, but we all did great. Too far apart puts them at completely different stages of development and managing toys and such gets more challenging (what is great for a 4 yr old is a choking hazzard for a 1 yr old).
I recall being very nervous about having my second, particularly as it related to my first, a boy just like in your case. I absolutely adore my son and didn't want him adversely affected by #2. I tell people that I think God plans those first months with the siblings in mind (baby sleeps much of the time and can't move around to disrupt the siblings toys and such). The development of the second gives you time to integrate them slowly. Does that make sense at all?
In short, whenever you are ready, go for it.
My best,
S. :)