This sort of inconsistency, while it may not be the fault of the tires, just doesn't lend confidence. I've heard many, many stories about street tires just suddenly going off, and that's a much more rare occurrence with track tires. Plus if you've ever run DOTs on the track, you'll know how much more grip and feel they give you.
Also, while I use A/B/C as a general rule of thumb, there are fast tracks and slow tracks and fast groups and slow groups. I've done days on my SV where I was at the top of the A group, and I've done days where I've spent all day in A being passed and never passing anyone. Which is why I recommend moving up tire compounds earlier, rather than later...it makes sure that you have the best suited tool for the job.
I hate this comparison more than anything else. I know that Colin edwards got within 8 seconds of his best on his motoGP bike on the old Pilot Powers. That doesn't mean that it's a good idea for a new rider, who's still expanding their personal limits. You're talking about people with decades or more of experience riding and racing, who are able to extract that level of performance out of a tire. Someone who's been riding for a couple of years, may have upwards of a hundred thousand miles under their belt, and you're comparing their performance to that of a seasoned racer? It's absurd.
Riders like Ken Hill, Berto, the guys who are rocking the front row of the AFM grids can do amazing things on subpar hardware. That doesn't mean that it's a good idea for one of us to be doing that. You have to realize that Ken Hill, at 1:56s, is pulling times that for him are an eternity off of his personal bests there. Is it fast by our standards? Absofuckinglutely. But he's extracting every bit of traction out of that tire and more, probably sliding it around a fair bit, and playing with the limits of traction in a way that's hard enough to explain, let alone replicate. He's pulling laps that probably feel a lot like warm up laps to him. He's got the lines, he's got the throttle control, the brake control, the lean control, and a thousand and one other factors that go into a fast lap besides the tires that a new rider simply doesn't have.
Again, just my 2c. If you're going to go to the track, it would make sense that you bring the appropriate tools. Just because Ken Hill can drive a railroad tie with a framing hammer doesn't mean we should ignore that we also have sledgehammers available.
Roytmani, I've run on a wide variety of bikes at the track, and I still really don't think it's a good idea to run street tires when you start to up the pace, regardless of size and construction. You don't compare the performance of a world class rider to that of a trackday noob in any other realm, why do people think it's a good idea to do that with tires? It's like saying "Just brake less and gas more and that's how you get a fast lap". Sure, it's the truth and it's how you do it, but it's not helpful, and it's likely to end up with someone on their head as they accidentally, rather than intentionally, exceed the limits of the tires and their skillset. I've drifted around the track on a roasted SC2 before, and I learned a lot, because it let me lose traction way before my personal limit. I'd guess it feels much the same for the fast guys to roast a street tire on the track...they're finding that limit of traction way before their personal limits would be kicking in, so they're able to focus and extract the maximum performance out of the tire while maintaining excellent consistency and technique as they ride.