I'll add my concurrence to the above commenters. I've also run staggered and square on the track - I think most track day folks will notice a difference with the sizes they end up going to; whether staggered or square. While not intentionally testing the various setups (stuff was on order during the summer last year; which is track day season), I ran three different setups.
1. stock with OEM Dunlops; and experienced a fair amount of understeer on exit - and entry when I overcooked it (driver error). Wear on tires is incredible in this configuration - and of course staggered gives you no real options for rotating other than flipping the tires around on the rims to wear the other side of the fronts (which is of good use on the road but useless on the track as you're going to spend a big portion of the time on the outer edges of the tires during cornering.
2. square tire set up with the stock rims. I got Pilot SuperSport 275/35x20s all around for the increased treadwear rating and the price. I ran a track day with this and it was definitely less understeer due to the increased rubber up front and decreased width in the rear. Again, my driving is the main issue, not so much the tires; but under the same conditions (my consistent mistakes), it pushed a lot less. I will say that overall grip was down on the Michelins vs the Dunlops - but this is a function of the treadwear rating and construction. It still corners like its nobody's business and I had no problem staying with OEM-equipped GTRs in the turns/sweepers.
3. Square set up tires on 10" Enkei GTC-01s; which finally came in late in the season. Even better turn in on these rims, if not a stiffer ride than the stock wheels. I didn't notice any appreciable difference in handling other than the car seemed a little lighter on its feet. Unsprung weight is reduced about 65lbs total with this set up, but would never pretend to 'notice' 65 less pounds in the car - my butt isn't that good.
BL - certainly more rubber in the front (proportional to the rear) is going to mitigate inherent understeer, that's just physics. As the wise gents above said, however, much more to do with one's skill and technique than the suspension/tire set up. That said, I prefer the square set up for the same reasons as these guys - more life out of a set of tires (they're my daily summer tires) because you can rotate them; and a little less push on the track without any big sacrifices in overall grip. If you can afford it, I'd go square. There are about a zillion opinions on this forum on what size to square it up with - I leave that to you.
