Depends on your definition of quick. I personally was highly disappointed with the power of my 05 stock, but I was told that on cool days they run much stronger- the tune is pretty rich on the cars stock, so that would explain it. People compare to mustangs all the time and say the GTO is faster, etc.- yes, it is- but I have seen several stangs run very good times with minimal mods vs. very few GTO's run strong (although there are a lot out there that do). I think the GTO is a much better built car and has gobs of potential, but for me personally, I felt it left a lot to be desired in stock form. I have since installed a procharger and some other minor tweaks and just put down 547 hp and 456 tq. to the wheels monday night- through stock manifolds, cats, etc.- so it is much better now . Still gets beat by some of the imports around here though haha. Weight and IRS kicks the GTO's ass when it comes to the 1/4 mile, but it makes a great road car- handling is decent for it's weight, top speed is impressive and they are nice and smooth to drive.
If you have the software and knowhow- it is just a couple clicks of the mouse. If not, then just get it tuned by any of the reputable shops out there and you'll be good or pick up a handheld programmer (last resort IMHO).
If you know what you are doing, it is fairly easy to extract power out of t a turbo 4. not to mention, you are working with a lighter car so it doesn't take as m uch. My car did 546 to the wheels and gets walked by a ~450 whp Integra from a 2nd gear roll. I start to pull on him up around 120ish.
When you're talking about "is the GTO quick" as compared to another car, isn't it pointless to talk stock GTO versus modded whatever? To say that a heavily modified ricer would beat a stock GTO says nothing about anything. If you were talking heavily modified GTO versus modified ricer, then you have something. Something tells me that if I dumped the $5,000 that Johnny Honda dumped into his rice rocket into my GTO, there's nothing to talk about.