Having abandoned the team that nurtured him for six seasons and secured him a world championship in 2008, Hamilton's switch to an outfit that had underwhelmed in its three seasons since buying Brawn GP in 2009 had appeared fraught with danger.
He was smiling on Sunday after the positive signs from winter testing translated into a solid weekend at Melbourne's Albert Park.
The 28-year-old had landed third place on the grid behind the two Red Bull cars after qualifying sessions postponed from Saturday were wrapped up only on the morning of the race.
Although blown away by Lotus's winner Kimi Raikkonen and shaded by the Ferraris and Red Bull's Sebastian Vettel, Hamilton saw enough in the Mercedes F1 W04 car to feel confident of challenging the front-runners.
"Really happy. I think it's way better than we probably ever expected on the first race of the season," Hamilton told television reporters.
"It was great and the car was feeling really good so I don't really know how the other guys were pulling away so quickly. But we will keep pushing and hopefully we'll get there."
Hamilton's fastest lap of 1:29.274 was still nearly half a second slower than Raikkonen's and another four drivers, including Toro Rosso's 12th placed Frenchman Jean-Eric Vergne, had quicker times.
"I've got to go really look at the data and try and figure out with the guys where we were losing time, but the car was feeling good," Hamilton said.
His team mate Nico Rosberg had a darker day, coming to halt on lap 26 with an electronics failure, which followed a gearbox problem during Friday practice.
Mercedes' troubles paled next to those of McLaren, however, who were badly off the pace and saved from further blushes by the craft of ninth-placed Jenson Button.
There was no delight in McLaren's woes for Hamilton, although the Briton did permit himself a gentle pat on the back for joining Mercedes.
"I think our position and how the car's behaving and how I feel in the team just confirms to me that I feel like I made a good choice," Hamilton said after qualifying.
"I never looked back once I made the choice and I didn't have any regrets about it."
McLaren were sure to hit back, he added, diplomatically.
"I don't know what difficulties they're having but they had a fantastic car last year, so I have no doubts they'll pick it up," he said.
"Sometimes in the team when I was there we had rough starts but the team are very strong at putting it back together."