Time will tell whether the 2008 world champion has taken a wrong turn or made the right move but, apart from careering into a tyre wall on his first day of testing, the early signs look promising.
Some remain convinced that the Briton will not be a title contender this year, and might not even win a race for his new team, but others are having second thoughts ahead of next week's season-opener in Australia. The man himself is sure he is on the right track and could be on to a winner.
"It's not 'no chance' and not definitely 'we will'," Hamilton said of his title prospects after he wrapped up testing with a time a second quicker than the race lap record at Barcelona's Circuit de Catalunya.
"We will definitely be able to win a race at some point," added the 28-year-old Briton, whose 21 grand prix wins have all been for McLaren - the team that backed him as a boy and gave him his F1 debut in a stunning 2007 season.
The debate over whether he was wise to turn his back on regular winners and title contenders for less competitive rivals is sure to rumble on for months to come, particularly if the new McLaren makes a strong start and the Mercedes eats tyres like it did last year.
Hamilton has said that the main target is to be competitive in 2014, when the regulations change significantly, and anything before that comes as a bonus.
How much he really believes that, and how much patience he has, is a moot point but the pressure will be much more on the team to deliver than on a driver whose talent is beyond doubt.
"There is everything to play for still. We won't know until the first race but don't be surprised if we get to the first race and we are not at the front. We are going in the right direction though," he said last weekend.
Testing times can be misleading, and Mercedes flattered to deceive last year, with one-lap speed not necessarily translating into performance over a race distance.
There is a suspicion rivals have kept their powder dry but there is no question that the new Mercedes F1 W04, after initial teething problems, is an improvement on last year's model.
Mercedes have had three disappointing seasons since they bought the championship-winning Brawn GP team at the end of 2009 and renamed it as the works outfit.
Germany's Nico Rosberg won in China last year - the team's sole success to date - but it proved a flash in the pan, with compatriot and seven-times world champion Michael Schumacher retiring with just one podium for Mercedes in three comeback years.
The team ended the season in Brazil with a car lagging the leaders by a considerable distance but with the morale boost that comes from having signed one of the quickest and most exciting drivers on the grid.
Some said the move was all about money, and the private jet Hamilton has acquired shows there is plenty of that around, as well as the freedom to build his own 'brand'. But his behaviour since he arrived at Mercedes, despite management upheaval, has indicated that he is in a happy place both on and off the track.
The Englishman has, in metaphorical terms, grown up and left home. Like Jenson Button when he moved to McLaren from Brawn in 2009, he has a new challenge and doubters to prove wrong.
Hamilton's gamble, if it is one, is nothing like the decision made by Canada's 1997 champion Jacques Villeneuve when he switched from multiple title-winners Williams to newcomers BAR in 1999.
Mercedes, a much more recognisable brand than McLaren beyond the confines of Formula One, have the resources and expertise to deliver. They may also have a big advantage next year with the new V6 turbo engine being introduced.
"I don't feel any expectation," Hamilton told reporters in Barcelona last week. "If anything I feel like I've got a free ticket.
"It's a year where we know that we may not have the best package but it's a challenge for me.
"That's for me to enjoy. It's not pressure from outside. The pressure is all on the other guys who have great cars which have evolved into this year's car. The pressure is on them to compete and perform. We only have everything to gain."
Ferrari's Fernando Alonso, Hamilton's former McLaren team mate and a double world champion, would be the last to write off the Briton's chances.
"Who is the strongest opponent, the strongest driver on the grid? Who is the one you have to keep an eye on? It is Hamilton - and it will still be Hamilton next year," the Spaniard told reporters back in January before any of the new cars had turned a wheel.
"I am sure he will be able to win. He is a super good driver because he won every year with any car. He won in 2007 and 2008. In 2009 they started around two seconds off the pace with McLaren and Hamilton was able to win races. And it was the same in 2010," he added.
Alonso, who spent one difficult year at McLaren in 2007, had no doubt when Hamilton announced his departure last year that the Briton had made the right decision.
He cited his own example and that of four-times champion Alain Prost as evidence of how beneficial a change could be.
Hamilton would agree with that.
"I'm happy I've got a new challenge, happy I've got a new start, happy it's a fresh chapter in my life," he said at the first pre-season test last month.
"Happy and excited because I know I can contribute and with a lot of hard work and perseverance I think we can get there."