I bought my new '07 FJR last year and now count myself fortunate that it came installed with Z6's as OEM. I put 12000 miles on these tires last year in all kinds of weather and road conditions. For about 80% of those miles the bike was loaded with 100 - 125 lbs. of camping gear and I weigh about 230 myself. The front tire definitely needs to be replaced; the tread is worn out and there is some cupping but the carcass/structure is still intact. I could probably go another 500 or 1000 mi. on the rear tire but I'll replace both at the same time when I put the bike back on the road in March.
Whenever I tune into this thread, I'm always amazed reading the posts where guys are braggin' about getting 4000 or 5000 or 6000 mi on a set of Bridgestones, Avons, Dunlops whatever. That's not even close to the Z6s and according to some of the reviews I've read, I'm not the only one getting both great mileage and performance from these tires. In fact, I've been meaning to put up a post with some pics called "Metzler's Don't Get No Respect" and I'll do it as soon as I get a bit of time.
The Z6 Interact is a new tire that replaces the Z6. Metzler promotes it as an "evolution of perfection", an oxymoron if there ever was one. Putting the marketing ******** aside, apparently they've tweaked the steel belt and rubber compound and I just hope they've made the tire better. You probably won't find too many riders who've had a chance to give it a long term tryout though.
These new Z6s will be my replacement tire. I'm not even looking at anything else.