Another concern I have is that both the GTO and the V seem not to be the most reliabe cars on the planet.
From a reliability standpoint, both cars are fine. Remember, a lot of people on forums don't post "hey, I've got 20,000 trouble free miles on my car." They usually post to express a problem or concern that they're having. You also get a lot of people who beat the snot out of their cars, like drag racing a CTS-V, then bitch that the back end blew out after repeatedly dumping the clutch at 5000 rpm -- then hopping the wheels for 500 feet. That's the car's fault?
As for the CTS-V vs. the GTO, I shopped the CTS-V a couple days before pulling the trigger on a new GTO. While the CTS-V does have the features you described -- the GTO offers the same performance, without the electronic doo-dads, for a lot less money. Even with a low mile used CTS-V, you're still going to have a lot more depreciation than with a GTO. And even though the CTS-V costs a lot -- its interior, particularly the dash, is pretty cheap looking.
The LS6 is a good powerplant. However, the CTS-V's shifter really stinks -- and there isn't a good aftermarket shifter for it that I'm aware of. If you don't like the factory wheels, then you're kind of hosed because of the 6-lug design.
Another thing I like about the GTO is that you do all kinds of cool things to it with Holden factory parts. I swapped out the tails with a set of Commodore VX SS ones -- and they look awesome. Installing a set of side marker lights as soon as the parts come in from Australia. Stuck a Pontiac SAP grille in, too. You simply don't have the options to personalize a CTS-V like that.