It doesn't tramline at all, really. Much better than say, my E46 328 with big summer tires on it. It's very relaxed at highway speeds, really, especially when you consider how quick the steering is, the big tires and how stiff the thing is. Must be an upshot of the new front suspension as the E46 had similar alignment with more rear toe-in.
I hear you about finding one in good shape. Looked at so many promising E46 M3's and E39 M5's that turned out to be disappointments before finally just biting the bullet and buying my car new off the lot. I can vouch that no-sunroof is the way to go, plenty of headroom with a helmet unlike our 335xi which rubs the top of the hat