Team-mate Kovalainen added: "I'm fortunate enough to have watched behind the scenes as this year's car has taken shape and I've been amazed at just how hard everybody has worked.
"With so many new rules, adapting quickly will be essential and I feel more prepared than ever for the new season."
Test driver Pedro de la Rosa will give the McLaren its debut in a private test at Portugal's Algarve circuit on Saturday - the first of a series of critical tests before the start of the new season in Melbourne, Australia on 29 March.
Ferrari, Renault, Williams and Toyota - whose car was unveiled on Thursday - will join McLaren at the new Algarve circuit in Portugal next week.
Renault, fourth last year, and Williams both launch their cars at that test on Monday, while BMW Sauber - third overall in 2008 - have chosen the Valencia track in Spain for the first public appearance of their new model.
All the new cars have been designed to conform to the biggest set of F1 rule changes in 25 years, which are aimed at improving racing and making overtaking easier.
The Algarve test will be the first time Hamilton has driven an F1 car at speed since clinching the title and becoming F1's youngest ever champion in Brazil last November.
Hamilton and Kovalainen pose with their new F1 challenger
He has done a handful of publicity appearances and other engagements since then but has spent much of his time having a break from F1 with his girlfriend Nicole Scherzinger, singer with pop group the Pussycat Dolls.
Following the unveiling of the Ferrari in Italy on Monday, much attention will be paid to how the McLaren compares.
New rules have forced modifications which lower and widen the front wing, and demand a tall, narrow rear wing.
Slick, untreaded tyres will also be reintroduced after 11 years on grooved tyres, and teams have the option of employing a kinetic energy recovery system (Kers).
The Kers system stores energy that would otherwise be wasted as heat during braking, then reapplies it during acceleration to provide a boost in power, controlled from the cockpit by the driver.
And Hamilton supports the changes to the regulations, saying: "I think it's important that F1 keeps moving forward and it's always been tough to overtake in the past so we need to get some of our competitiveness on the circuit back.
"Hopefully with the slick tyres, less downforce and Kers we'll be able to do that."
The fashion so far has been for a tightly-waisted rear to the car, to ensure effective airflow to the rear wing - with Ferrari's particularly narrow. McLaren's new challenger is expected to follow that trend.
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