BlackBerry's upcoming 'BB10' operating system has garnered rave reviews in advance of its Wednesday launch - gadget fan Jonathan Ross describes it as "the most impressive new phone I've played with."
Stephen Fry - another early tester - said that the new operating system offered "amazing features."
The 'new' BlackBerry offers 'personal' and 'work' modes, and a 'flowing' approach to switching between apps.
The first handsets are touchscreens, rather than QWERTY handsets - a radical new move from the smartphone pioneer.
Shares in RIM, the Canadian company behind BlackBerry, have surged in advance of the launch, more than doubling in four months after falling to a low of $6.22 in September.
BB10 is widely seen as a 'last chance' for the company. Its PlayBook tablet was a flop, and the company's market share in smartphones dropped from 40% to 4% in just four years.
BlackBerry is to spend a reported £2.3 million on a single 30-second advert during The Super Bowl - part of a global marketing drive for the new operating system.
Gadget review sites have been enthusiastic about the new operating system, which will be used in six new handsets by the end of the year.
TechRadar said, "We were impressed with how smooth and slick the interface felt under out fingers – the gestures work very, very well after a few minutes, the powerful messaging ecosystem is still there and even the on screen keyboard is great.
"It's a bold move, and one technophiles will love. If the hardware is decent too, there may be enough BB fans out there willing to use the finger-flicking platform... but with so many things to learn, it will take some serious and quick eduction to get users up to speed."
The OS is designed to allow users to hop easily between applications using gesture control, and access information such as new emails far more quickly than rival OSes iOS and Android.
Jefferies & Co analyst Peter Misek, said recent trials of BB10 test devices showed vast improvements over its existing smartphones.
"Recent tests and demos have shown a solid browser, smooth touch interface, and intuitive navigation. We now believe the operating system performance could be better than or equal to Android Jelly Bean and likely on par with iOS 6," said Misek, referring to the latest versions of software powering Android and Apple devices.