On my 2003 M45, I have Bridgestone Turanza ER33 "performance tires" as delivered from Infiniti in a 234/45-18, WR rated. My initial impression of this tire was that it was an unmitigated disaster. They were incredibly noisy and very squirelly on curves. And, I was getting lots of black rubber dust on my car sides. I almost couldn't wait to get them worn out and replaced!
But, after the initial 1/32 - 2/32" of tire wore off (about 1000 miles or so), the tire performance has improved dramatically. There is no more rubber dust, and the grip and noise has improved a lot. Still not as good as other tires I have used, but much quieter and grippier now. I guess that the car sat at the dealer before being sold, and the tire was not exactly helped by this delay!
Now, I rank these tires as "decent", although I have not used them in wet weather yet (my personal concern for tires). After they wear out (which I expect in about 12k miles or so - given the tread wear so far), I will still change them for some other brand/model and size, but I can say that these are not as bad as I first thought!
It is really too bad that the Firestone Firehawk SZ50EP's are not made in a 18" size.