I've had no problems with water getting in unless it was REALLY coming down. But it's still no problem given where the water is directed like stated. It keeps the heat out, and the front driver vent cann even feed your CAI if you like.
I clean my engine compartment usually every 2 weeks or so anyway, so there is absolutely no detriment and nothing to be concerned with. Also the nice thing about this hood is you really dont need hood pins. It's held downn very securely. It's the only carbon fiber hood that doesnt suck. It adds a lot of visual appeal as well. I get a lot of compliments.