Well, I'm a girl, and this is my name so I'll let you know how I feel.
I think Jamie is absolutely adorable on a boy. If it wasn't my name, even though I'm spelled differently, I would use it in a heartbeat. However, if you spell it Jaime, he will be constantly correcting people his whole life as in "No,not HIE-may, JAY-mee." And he will have to spell it out and deal with people mispelling it any way.
It's beyond tedious. So, while I love Jamie, if you're going to name a boy that, give him the small mercy of having the easily recognizable spelling.