Now, I'm not going to pretend that we did it for any other reasons other than coolness factor, but you can feel and see the heat pouring out of the vents after running the Jeep for even only a short period.

As far as any rain factor goes, when you consider how much rain is kicked up into your engine while driving (especially through rivers), it shouldn't make too much difference.  If it gets to be an issue a drip pan would work, or just a piece of sheet metal to shield the alternator would work, but being that this is AZ, it won't be an issue for much of the year.  While driving it should blow right past anyway.  It is cool though being able to see his engine through the hood.

The only thing I'd add to the install is to make sure to apply the 3M tape along every outside edge or there will be a slightly visible gap where you missed.  Other than that hardly noticeable detail, the install went extremely well.  But most importantly, Jared was extremely happy with it and was able to sleep better now that it was all said and done.