I haven't yet done one on my current car, but I had the exact same engine in my hatchie which did have one...

The pros:

More effecient combustion of the fuel air mixture which will give you slightly better gas mileage, and a slight pick up in horse power (these things are multiplied with forced induction, porting & polishing of the head, bigger injectors, fuel mapping changes, etc...except for gas mileage)

The con:

The biggest con, to me, was the fact that you are dependant on the companies rep to ensure that you don't get stuck somewhere. I had my coil go out one night and ended up having to get my hatchie towed home...that night sucked.