Even in the ultimate form in which we tested it - the most powerful engine, a variety of expensive options and the Evolution Panorama AMG upgrade package - there is considerable subtlety in the way the Mercedes C-Class Sports Coupé goes about its business.To begin with, it does not look overtly sporty, though the Manx cat-like chopping of the tail, which gives a very similar effect to the one BMW achieved with the first 3-Series Compact, looks more elegant in real life than it does in photographs.Nor is there anything about the sound of the engine to suggest that this is a performance car. It's almost as if Mercedes had deliberately suppressed all the interesting noises the four-cylinder 2.3-litre unit might have made, just in case anyone got too excited about it. To take an example from recent experience, a 1500cc Kia sounds about ten times more evocative.You could drive the Coupé for a long time without getting any hint of the performance available. And yet, with its almost silent supercharger (the Kompressor of the car's title) to force air into the system, this is actually a very purposeful engine.Maximum power is 197bhp, but more importantly there is a heap of torque all across the rev range. It's not obvious unless you push the throttle pedal well down, but if you hit a damp patch of road even when apparently not driving hard, the traction control warning light reminds you that there's a lot more going on at the rear wheels than you might imagine.The AMG package, which is largely cosmetic, includes sports suspension, larger wheels and tyres, but again there's no real sense that this is an overtly sporting car.Boy racers, therefore, need not apply. But I quite liked the Coupé's unobtrusive character. If you want to potter around gently, it does that very well. If you want to go quickly, it's very good at that too - superb mid-corner grip is followed by a real surge on to the next straight as the supercharger starts doing its stuff. Add in a very comfortable cabin in classic Mercedes style, and you end up with a car that in most respects I'd be very happy to live with.But there are niggles. One is minor but inherent, the other major but a £650 option which can be ignored.The first concerns the shape of the car's hindquarters. Combining a swooping roofline with a lower-body wedge shape results in a very shallow window which limits rear visibility. Mercedes has got round this by adding, underneath the spoiler, an extra window - not a large one, but enough to increase the vertical glass area by enough to make all the difference.It's a very similar tactic to the one used by Audi for the little A2, and it gives rise to exactly the same problem. A vertical piece of glass at the back of a short car picks up an amazing amount of dirt, and there is no way of wiping this clean on the move (you couldn't possibly design a wiper that would clear it). In bad weather the lower window becomes opaque almost immediately, which leaves you with the same visibility problem you had in the first place.Niggle number two is the Sequentronic gearbox option. Normally the Coupé is available either with a six-speed manual transmission or a five-speed automatic. Sequentronic is simply a way of controlling the manual box electronically. Depending on the mode you choose, you either select the gear you want by pushing the short but well-weighted lever forwards or backwards, or you let the software decide for itself when to make the change.Either way, the mechanical process is exactly the same as for an ordinary manual - release clutch, shift from one ratio to the next, re-engage clutch. This is a time-consuming process, but normally you don't worry about it because you're the one doing the work. When Sequentronic takes on the job, and you're sitting there waiting for everything to happen, you become very conscious of the car not making any progress for a second or so in each change.If you're keeping a constant throttle, which is the natural thing to do, the delays are very irritating. You can get round this by easing off the pedal while the changes are taking place, and this also has the effect of making the changes much smoother. But in automatic mode it's not easy to second-guess when they will happen.My eventual solution was to opt for the manual change every time. Effectively the car was now an ordinary manual with a clutchless change, and history tells us that this is not a popular choice among buyers - Saab and Renault both tried it a few years ago, and sales were so bad that they both gave up.Using my own money, I'd stick with the standard six-speed manual. And speaking of money, beware of the apparently attractive list price of £23,250. With the AMG pack, Sequentronic, leather upholstery, a six-disc CD changer and metallic paint, the test car totalled £29,190 on the road, which is a whole different ball game.Second opinion: Yes, this is a serious performer, and probably quicker point-to-point than the bald figures suggest. There's something invigorating about feeling a supercharger take hold, although I appreciate that people brought up on turbochargers miss the dramatic sound effects, and maybe the non-seamless boost. I'd certainly skip the Sequentronic option. The conventional Mercedes automatics are top class, but I just don't see the point (in any make) of this kind of halfway-house system, when you feel the car almost semi-stall partway through each gear change. Give me the six-speed manual or the normal five-speed auto - and that's quite a difficult choice to have to make. The Panorama pack includes two glass roof panels, front and rear, and the slide-forward blind arrangement is another example of how subtle this car is. A single switch brings forward, not the usual kind of perforated semi-transparent material, but something like proper saloon-car roof trim. Ross Finlay. Engine 2295c, 6 cylinders Power 197bhp Fuel/CO2 29.1mpg / 231g/km Acceleration 0-62mph: 8.0 seconds Top speed 149mph Price £23,250 Details correct at publication date