I also just picked up a set for a 2011 GT:
Please excuse the bad lighting and half-complete splitter.
For something that should perform almost as well as a Tiger Racing hood and costs significantly less (especially when you consider paint), I think this is a great option. The louvers themselves look pretty well made, but on the car, they look a bit "out of place" to me. However, for this car, I don't care. I wouldn't add them to a daily-driver, but of course to each their own.
Before installing these, I watched Grassroots Motorsports's video on installing them, and I think that's what ultimately drove me to buy them. It was really comprehensive, and it had me sold. Technically, these are not hard to install, but it really helps to have two people. I removed the hood from my car (a two-person job) so I didn't have to worry about cutting something, and I put some paint on the bare metal before installing the louvers. Even with the hood off the car, I needed help putting the washers under the rivets. I don't think a pneumatic rivet gun would have allowed me to do it myself. My arms aren't long enough, and since the rivets are kinda cheap (one of the mandrels fell right out of one of mine), I wouldn't want to risk it. Also, I think I took way more time aligning the templates compared to them. It's deceivingly difficult to draw straight lines on a long, curved surface. I'm still off by ~1/8", but probably I'm the only one who will notice. Overall, I probably spent 3-4 hours on the whole job, but if you're not as OCD as me, you can do it in 2 hours.
I'll see how much of a difference these make to coolant and oil temperatures on-track in about a month...