While Kimi Raikkonen's night-clubbing antics have given McLaren cause for concern, team mate Juan Pablo Montoya has so far exceeded his new employers' expectations.
Chief executive Martin Whitmarsh praised the Colombian after the launch of the team's 2005 Formula One car.
"We are, I guess, very much in the honeymoon period with Juan Pablo, and it may be this is the style of relationship that we'll always have with him, but we don't know," he said.
"But it's been extremely positive on all levels.
"I think he's exceeded our expectations in regard to his technical capability," added Whitmarsh, who earlier faced questions about tabloid reports of Raikkonen's alleged drunken behaviour in a London lap-dancing club.
The Colombian, who won the season-ending Brazilian Grand Prix for Williams last year before replacing Briton David Coulthard, has thrown himself into fitness training.
"I do feel at home here, to be honest," he said.
The team said the 29-year-old had shed six kilos between his first test with McLaren in December and last week.
"He is training with a McLaren trainer harder than I believe he ever has before," said Whitmarsh. "People said he won't train, he's not motivated in that direction and the guy is absolutely delighted by how fit he is.
"He's done 200 laps last week and got out of the car saying: 'I feel fresh as a daisy, I've never been this fit before' and I think that's a great testament to his enthusiasm at the moment."
Whitmarsh said the team had expected Montoya, whose wife Connie is expecting their first child, to be a quick driver and he had proved that soon enough.
But he had also impressed them with his focus.
"He's also...the sort of driver who would go away and come back the next day and it would be quite clear from what he said, and the observations, that he had been thinking about the day before and analysing it and really working hard to improve the car and improve the team and himself.
"Thus far, contrary to some predictions from the outside, it's been fantastic working with him but it's early days yet. When we get into the heat of battle things will go wrong on both sides and we'll see what happens."
