The massive SUV priced from €170,000 (RM774,000) at home in Germany is close to the striking concept version shown last year and represents the most powerful M-badged car ever from the Munich marque, with a beefy hybrid petrol-electric drivetrain.
It is only the second stand-alone M model since the legendary MI sports car of 1978. An even sportier Red Label variant of the XM is now in the pipeline.
Aware of its controversial visuals, BMW said the XM has a "strikingly unique exterior." Germany's Auto Motor und Sport magazine called the it a "monster SUV", but admired the performance.
"The fact that 44 years after the M1, M GmbH presents a chubby fairy in extroverted SUV garb complete with gold tinsel and more than twice the kerb weight is compensated for by the mighty performance," said the industry mag.
Dubbing the XM a "heinous heifer," automotive news website CarBuzz was less kind. "It's still ugly, but if we're being honest, the production version is slightly less offensive than the Concept XM on which it is based. Don't take that as an endorsement - the XM is still sickeningly painful to look at."
The illuminated kidney grille and snazzy gold wheels do give the 2-7-tonne XM behemoth a vulgar look, but there is no doubting the power on tap.
An updated version of BMW's twin-turbo 4.4-litre V8 pushes out 483hp and massive torque. Total system output is 644hp.
"The trouble is the BMW XM is cartoonishly ugly. It's a cacophony of design elements and details that don't really tie together," writes Tyler Duffy in the consumer website Gear Patrol.
UK gazette Autocar was among the more favourable voices, calling the XM "truly new and different" and the latest in a stunning series of impressive models launched to celebrate BMW M's half-century.
The XM is a far cry from its elegant namesake, the Citroen XM saloon made from 1989 bis 2000. The Bavarian brand had reached an agreement with the French badge over using the nomenclature.
Auto Motor und Sport concluded its review by saying the XM is not really designed for the German market - where oversized SUVs have drawn criticism from climate activists. It is aimed instead at customers in the United States, China and Arab countries.
