Very true indeed. Other than Senna I can't think of a driver doing so well in a new team. Roll on Canada
Starting in 1980 (round number, and after most drivers participated in multiple series and frequently switched teams), I've compiled a list of drivers who won in their first season with a new team.
Carlos Reutemann: 1980,
Williams
Didier Pironi: 1980,
Ligier
Alain Prost: 1981,
Renault | 1984,
McLaren | 1990,
Ferrari | 1993,
Williams
Keke Rosberg: 1983,
Williams
Niki Lauda: 1982,
McLaren
Patrick Tambay: 1982,
Ferrari
Riccardo Patrese: 1982,
Brabham
Rene Arnoux: 1983,
Ferrari
Michele Alboreto: 1984,
Ferrari
Ayrton Senna: 1985,
Lotus | 1988,
McLaren
Nigel Mansell: 1985,
Williams | 1989,
Ferrari | 1991,
Williams* | 1994,
Williams*
Nelson Piquet: 1986,
Williams | 1990,
Benetton
Gerhard Berger: 1986,
Benetton | 1987,
Ferrari
Thierry Boutsen: 1989,
Williams
Damon Hill: 1993,
Williams | 1998,
Jordan
Jacques Villeneuve: 1996,
Williams
Michael Schumacher: 1996,
Ferrari
Heinz-Harald Frentzen: 1996,
Williams | 1999,
Jordan**
Johnny Herbert: 1999,
Stewart
Rubens Barrichello: 2000,
Ferrari
Juan Pablo Montoya: 2001,
Williams | 2005,
McLaren
Giancarlo Fisichella: 2005,
Renault
Felipe Massa: 2006,
Ferrari
Kimi Raikkonen: 2007,
Ferrari | 2012,
Lotus
Lewis Hamilton: 2007,
McLaren
Fernando Alonso: 2007,
McLaren | 2008,
Renault* | 2010,
Ferrari
Heikki Kovalainen: 2008,
McLaren
Sebastian Vettel: 2009,
Red Bull
Jenson Button: 2010,
McLaren
* If you include drivers returning to a team they had previously driven for.
** Heinz-Harald Frentzen managed the feat of winning in his first seasons in two different teams, but he only won three races in his career.