Having just come from 6 years of owning a GTR, with lots of time on track..... yes they are silly quick on track, but they are a GT car first, so it would depend on your goals. If you are intent on being the fastest thing out there and cost is of no concern, then yes the GTR is going to be good. If, however, you don't care too much about being the fastest and its more about the fun aspect, the GTR is not the car for you.
I also ran a non supercharged MX5 (MK2) as a track car and that was a lot more fun than the GTR on track. When the MX5 got a SC it went from being the slowest (on small tracks) to only being passed by R8 V10s and GTRs and it was absolutely awesome to drive on track!!
If like the rest of us, you want a car that is good at a mix, then the GTR is still very good.... long road trip over to Europe (Transalpina, Transfagarasan, etc) it is superb! It was an absolute pleasure and being able to drive the twisties and manage 190mph (derestricted) is just brilliant.
The costs of running the car though, are very high.... tyres, well I killed a branded new set of R888Rs in 1 day at Bruntingthorpe, so that's 1k... Brakes, I was running Alcon discs and RS29 pads. 2 sets of pads to set of discs on the front. Pads were about 450 for the front set and discs were about 6-700 for the front set. You will be amazed how quickly it all adds up, especially when you start adding things like gearbox coolers (2.5k), suspensions (litchfields 4k+) and god forbid the gearbox goes.... 8k to rebuild roughly (once damaged).
Personally, I would choose something old, reliable and fun - Datsun 240z, Ford Escort MK1, etc as the first car and then something like an Aston, C63 AMG or even a very big comfortable 4x4, etc as the second car.