I first tried these on my '77 GS550 and they felt great right away. Within 10 miles I was feeling comfortable enough to treat them as fully scrubbed in- these don't seem to need the break-in typical of most tires but use your own judgement. These tires give secure grip at an aggressive (remember it's a 38 year-old bike with non-folding pegs) pace- you'll likely run out of clearance before you run out of grip. They act like regular radials- less sensitive to rain grooves and uneven pavement. The front tire is wearing minimally while the rear had noticeable center wear within 700 miles from my (then) mostly freeway commuting mileage. At 3500 miles the rear is likely good for another 1000 miles while the front will go at least another 5000 miles from a wear standpoint.
These are expensive compared to other, more-than-adequate tires, but to me they're well worth it for the type of riding that I do. They're going on my '76 XS650 this week, and on my '86 SRX600 when the time comes.