I had this same question several months ago when I was deciding on a track wheel/tire setup. See the threads from Feb-March 2011 for more info. I was also concerned about a 275 in the front in terms of steering feel and especially tramlining, but more so if I used it on a daily driver/street setup.
I ended up getting Forgeline 18x10" wheels through Turner Motorsport and using 275/35-18 Nitto NT01s all around. It was fantastic for this last season, which was my first full track season. Compared to the stock 245/265 PZero setup, the Nittos are a revelation--much better turn-in, braking confidence, and overall grip. I had assumed this was due in large part to the larger contact patch of the wider 275s up front, but see Richbot's reply in my thread "BF Goodrich R1 size question" in the track/autocross section from a few days ago--he makes the argument that the overall contact patch size stays the same, and only the shape changes. The great improvement in front-end grip in cornering and braking is therefore probably more attributable to the Nittos' R-compound stickiness and tread pattern (or lack thereof!).
In any case, I've been happy with the 275/35-18 NT01 setup on this car. I have taken advantage of the ability to rotate the tires around. When I notice the driver's front tire feathering more on the outside than the other tires (need more negative camber next season
), I rotate it to the other side, and have also rotated front to back to even out wear.
I was curious to try the BFG R1 next season, and I would have just gone with a 275/35-18 square setup again, but I've seen that some people have done a 265/35-18 -- 285/30-18 staggered setup with that particular tire. That's why I posted the inquiry.