There are two ways of looking at this. You might think of the RS as the fastest and most powerful TT that Audi has ever put into production, and there could be no possible argument against that. But Audi looks at the matter a little differently, and is promoting it as its first RS model based on a sports car rather than on a saloon or estate.
Either way, the specification looks very impressive. The RS, which comes in both Coupé and Roadster forms and shares its part-steel part-aluminium construction with all other second-generation TTs, has a new 2.5-litre five-cylinder turbo petrol engine producing an unprecedented 335bhp. The Coupé is the quicker of the two and has a 0-62mph time of 4.6 seconds (top speed is limited to 155mph - or, at extra cost, 174mph - though the RS would go faster still if unfettered by the electronics) so in a straight line it's capable, up to a point, of matching the 4.2-litre V8 version of the R8 despite costing little more than half as much.
In order to compensate for the lack of a solid roof, the Roadster has extra bracing and a greater proportion of steel in its body construction - 42% as opposed to the 31% for the Coupé. This adds 60kg, and although the extra weight makes very little difference on paper (the 0-62mph time is barely greater at 4.7 seconds while combined fuel economy deteriorates from 31.0mpg to 29.7mpg), the Roadster does not feel like it has anything like the same punch. And I'm not saying that because I'd already become used to the power in the Coupé and was less impressed by it when I tried the Roadster. On the contrary, I drove the Roadster first and found the Coupé to be a lot livelier when I drove it later the same morning.
The brakes and suspension are more than a match for the engine, and since the RS of course has a quattro four-wheel drive system as standard each tyre has on average an unthreatening maximum of around 84bhp to cope with. In fact the distribution is more complex than that, and in a good way, since power is removed from overloaded wheels and transferred to ones that can better cope with it as the need arises.
For these reasons the RS generally feels quite subdued. In everyday driving it doesn't feel much different to a lesser TT, in the sense that you never feel it's going to do anything silly, and even when you're pushing harder it would take a spectacular effort to make the car behave badly.
The look is undramatic too. There are various styling add-ons to distinguish the RS from its stablemates - including new bumpers and a rear wing which has an air of Halfords about it and is so flimsy that I'd be surprised if it could be shown to be doing anything useful - but in general you would have to take a close look to convince yourself that this really is the most potent TT ever devised.
Similarly, the interior is nothing out of the ordinary (you get a similar effect in TTs costing around £25,000, which is shortly going to start looking like a very trivial figure), and as you've probably guessed this is all leading to a suggestion that the RS has a bit of a problem. I have no objection whatever about the pleasant road manners, but I was disappointed by a lack of the magic which you so often get with high-performance Audis. The TT simply does not feel special enough to be worth the £50,000 you will probably pay for it.
I say "probably" because although the list prices of the RS are much lower than that, at £42,895 for the Coupé and £44,885 for the Roadster, the versions I drove were both worth more than £50k, and the optional extras which were responsible for the hike are very likely to be chosen by RS buyers. That is most regrettable in the case of the 19" wheels and 35-profile tyres which replace the standard 18s. As is often the way with Audis, fitting larger wheels and silly rubber has a drastic effect on the ride quality which, to me, isn't compensated for by the more dramatic appearance. Audi's press fleet does not include an RS with the standard wheels so I can't definitely say that such a car would have a better ride, but I'd bet my house on it, and I would be the first to congratulate the fellow of wisdom and taste who bought one and resisted the temptation to cough up an extra £1200 for the 19s.
The cars I drove had different amounts of extra equipment but they shared non-standard paintwork, a Bose sound system, a CD changer, mobile phone preparation, uprated satellite navigation, special door mirrors (folding, heated, auto-dimming), cruise control and adaptive headlights. The combined cost of that lot is £4230, not including the cost of the "wrong" wheels and tyres, and there are so many other retail opportunities (race-style bucket seats at £1665, for example) that you can see how easy it would be to send the price well over £50,000.
So you could end up paying around five-eighths of the basic cost of a 4.2-litre R8 without ever experiencing anything like five-eighths of the thrill, and that really won't do. This is undoubtedly a very fine car, one which I can't really fault for its performance and behaviour, but it does not have the halo of greatness which surrounds other RS Audis, and for that reason I don't think it's worth the money.