The Infiniti M is a competitor to the BMW 5 Series and Mercedes E Class. As is usual with rivals for these cars, Infiniti says it provides buyers with an alternative to the default German choice in this segment. However, there is little evidence that people actually want an alternative to the Germans: apart from the Jaguar XF, no non-German rival saloon sells in decent numbers.
On the plus side, the Infiniti is certainly a much more serious attempt to compete than something like a Citroen C6, as it does have three big advantages. Firstly, it is Nissan's flagship brand, so its build quality is bullet-proof. Secondly, if you happen to live close to an Infiniti dealership (not very likely admittedly), you will be visiting the best dealerships in the business. Thirdly, and rather surprisingly, Infinitis do have a distinctive personality. They are all angled towards sporty luxury and provide more character than the equivalent Lexus models. Even the 3.0 diesel feels sporty: it has one of the most petrol-like diesel engines we have ever driven. Unfortunately Infiniti has tried so hard to make the diesel sporty, it has rather forgotten the point of a diesel engine in the first place. Its CO2 figure of 199 g/km is one-third higher than the Jaguar XF 3.0 diesel, which is going to rule it out for a lot of company car drivers.
Given its lack of economy, the M-Series probably makes most sense in S trim, which comes with 20 inch wheels and four-wheel steering that gives it extremely quick responses. That way you can best enjoy burning all the fuel. All versions share the same super-luxury interior which showcases all those clever electronics that Japan is so famous for. Certainly, it is a much more indulgent and sumptuous environment than the coolly logical interior of its German rivals.
Overall, the Infiniti M is a good car, but it is definitely a minority interest model. If you like the looks, the performance and the interior, go for it. It is not going to make you look stupid, unlike those dreadful Cadillacs that GM tried to sell in the UK until recently. However, the unknown badge and high fuel consumption will rule it out for most buyers.