Leading Formula 1 drivers were unanimous in their praise for the new United States Grand Prix circuit.
McLaren driver Lewis Hamilton described the Circuit of the Americas in Austin, Texas, as a "great track".
Hamilton and team-mate Jenson Button praised the high-speed first part of the track, which is modelled on Silverstone's famous Becketts section.
Button said: "The change of direction is faster than Silverstone and that's saying something. It's fantastic."
Hamilton added: "It is a great track to drive but the whole track is very difficult.
"It's very tough to get all the sectors together. I find the second and last sector the easiest. The first sector is the hardest with the high speed; there are several different lines you can take and it is massively quick."
Button was less enamoured with the unusual approach to Turn One, which has attracted a lot of attention because the track rises steeply uphill to the corner.
He complained that the surface of the track there was "not even - in certain places you have grip and in certain ones you don't".
And he said he thought that overtaking would be difficult because there was a series of corners into a slow hairpin before the track's longest straight.
"I don't think overtaking is going to be easy," Button said. "I think [in future] we need to find a mid-speed corner on to long straights not such a slow one, it's very tricky to stay with the car in front but it's fun to drive and I hope we can put on a good show."
The corner that caused the drivers most problems was the penultimate corner, Turn 19 - a downhill left-hander at which several drivers, including Button, ran wide.
Button added: "It's a mid-speed corner and you've come through a very long right-hander putting heat into different parts of the car, different tyres and then you turn into the left and the car's working differently.
"It's just a shock for the car, I think. The balance isn't quite what you expect, you don't have the balance you would expect and that's why you're getting oversteer and a few cars going wide there."
Red Bull's Mark Webber said: "It's quite blind on the apex so it's difficult for us to see the exact apex point and it just seems to be very, very slippery from apex to exit. A lot of us look pretty amateurish but we just refuse to believe there is that little grip."