The biggest draw back is that you will spend every waking minute trying to choose a color (I have since I ordered my car in January, lol... I finally had to chose one, I just hope I don't kick myself in the foot for it), and after that, trying to forget about the long wait till yours comes, lol (I made a custom advent callendar that ends on the day I get my S5, which is Spet. 29, so how lame is that, lol).
On a more serious not, I can't truly write the best reponse as I have not owned one, although I can try since I have driven one many times and reasearch it extensivly. Basically, there really is not much wrong with the car, as long as you are ok with its speed (some people may say "blah blah blah, the C63 AMG and M3 is so much better than the S5, blah blah blah," and that is only because they are speed freaks and dont understand the purpose of the S5). There are a few minor gripes that I have, for example: the Audi MMI nav does not support TMC-RDS traffic reports (which has saved my ass a few times when driving my friends BMW 335i), the S5 does not have any system comparable to On Star, MB SOS, BMW Assist (so if you car gets stolen, ur screwed, if you lock your key in the car, ur screwed, if you get into an accident and can't make a phone call to the police or are unconscious, ur screwed, and if you need to tow your car to service and don't have cell coverage, ur screwed, among many other benefits of these systems), if you want an auto tranny, there is no DSG available, and there are many options available in other regions of the world, like Europe, which are not available on US spec cars (like hill hold assist, 20' RS4 rims, Audi Lane Assist, rear elecric sunscreen, ect.), most of which I would have ordered. BUT, these things are usually minor... I don't get into traffic too much personally, I have never uses SOS in my dads MB, (except for when I got into a minor accident, which I could have used a cell phone anyways. Also, the chances that you will get into a serious accident are slim, and the chances you will get into a serious accident in which no one sees you and you are unconscious is 100x slimmer. Plus if you are still really worried, I am sure there are aftermarket items you can get like lojack with assist, or whatever), I wouldn't buy an auto even if DSG was available and I would rarely use any of those options, and I can just the the RS4 rims aftermarket. So, all in all, if you love the looks, are satisfied with the umph and these minor shortcoming don't bother you very much, then I honestly could not recomend the car more, especially for someone who lives in the east coast who sees lots of snow like me (and in that sense, the only other comparable car is the BMW 335xi coupe, which is great but doesn't have the looks or attractivness of the S5, plus there are so many 3 coupes and sedans, but very few S5s/S5s).
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