Swapped out the Cobra Chromes that came with my Rocket 3R at 4500Km after a slick bit of tarseal took me and the bike down (Certain NZ Roads are shite in the wet)
Fitted 888 Marathon Ultra's front and back. Got good mileage out of them. Just replaced the rear at 18000KM (Thats how many K's i got out of it) as it was a bit slick(Spun up nicely whenever pulling away!!). Front still has fair bit of tread to go.
Considering the torque of the beast these tires have surpassed my expectations. Summer time grip is great. Winter time.....well just ride to the conditions!
Its good to always read reviews but really at the end of the day it all comes down to rider experience, type of bike and road conditions