OK, here's my initial review of the Goodyear Eagle GTs:
First off, I got mine from Bob Penkhus Mazda at Powers Motor Park for $689 installed (it was actually $653, but they did a half-price alignment for me...). Went with 225 40 ZR18s. I kind of wanted 45s, since we have potholes galore around here, but I forgot to tell them that. They replaced my General Exclaim UHPs that wore out after...uh...11K miles.

Anyway, I put probably 50 miles on them so far, in around-town and highway driving, and a brief moment of off-roading (lol...see below).
First thing I noticed about the GTs was that they're quieter than the Exclaims. Way quieter. And they ride softer -- take bumps much less severely.
I also like the way they look -- aggressive, variable tread with a nice rim protector as well.
So far, I've only driven on dry roads with them, and while they're better than the Kumho Ecsta ASXs I had on my old 6, they're NOT as sticky as the Exclaim UHPs were. They're close--really close--but in tough turns they start to squeal a little sooner than the UHPs. There's one turn in particular, a sweeping 90-degree downhiller, on which I LOVE to push the MS6 to its limits. On the UHPs, when they had decent tread, I would get about an extra 5 mph out of them in the turn before they started to squeal. However, that could simply be due to weather conditions, surface conditions, etc at the time I tested the GTs. So I'll have to try it again a few times, but the results have been generally the same on the other turns I've taken with the new rubber.
Launching the car is different with the GTs than it was with the UHPs. With the UHPs, when they had tread, there was usually a little "chirp" and then the whole car jumped forward, often shuddering like the damn rear end was coming off. With the GTs, there's no chirp, no shudder, and a bit softer start. I'm betting that's because they're new and need some time to break in -- we'll see. It isn't necessarily a SLOWER launch...just a different one.
I did manage to do a quick slip test on some gravel on the side of Hwy 24 tonight. I was pulling off so I could turn around and head home, and ended up on some dirt and gravel. DSC was already off, so I gunned it. The GTs gripped MUCH better than the UHPs had on dirt or gravel, and it took a second or two to get the back end to break loose. Then I slid up onto pavement, and it only took the tires a second or two to bite the asphalt and right the car, even with DSC off. So at least on gravel/dirt, they seem like they're better tires than the UHPs. Not that I drive on those surfaces much...that's why we have a Jeep.

Hopefully we'll get some rain this weekend, so I can test out this allegedly GREAT wet-surface traction for these tires. Doesn't look like we'll get much snow this winter, but who knows? Maybe mother nature will cooperate...these things are supposed to have very good snow traction, as A/S tires go.