Seems to me some players have a critical opinion about the Scandi mostly based on the fact that White gains time on the queen with Nc3. Actually, White only recovers the tempo "lost" on his second move (exd5). Someone even called it "theoretically inferior" based on the first few moves. The Scandi is perfectly playable, and there are several strong GMs playing it regularly. Tiviakov, Kramnik, Ivanchuk, Karpov on his older days just to name a few, and even Carlsen has tried it out. The Scandinavian Defence - especially the 3...Qd6 variation - equalizes in almost every possible line against 1.e4. The "problem" (if there is one), is not the irrelevant Nc3 threatens queen discussion, but the fact that it can be difficult to win with lots of games with Black. At amatur level this is hardly a problem, because most players with White doesn't have a clue about how to play against the Scandi. At higher levels, the main line is :
- e4 d5 2.exd5 Qxd5 3.Nc3 Qd6 4.d4 Nf6 5.Nf3 c6 (also a6 is played, and GM Kovalenko's aggressive Bg4). Then only 6.Ne5 puts any pressure on Black. Earlier also 6.g3 was considered strong, but it has been well neutralized by Black thanks to the efforts of GMs Tiviakov and Kontronias.
After 6.Ne5 play goes: 6...Nbd7 and White has three main tries:
- f4 (Shirov's idea)
The Bf4 variation is not a problem anymore. Black equalizes quite easy.
7.f4 and 7.Nc4 is more challenging, but Black has found ways to maintain the balance and the theory of these lines are quite heavily developed. Playing Scandi (at least on a higher level) requires knowledge of these lines, and how to handle these quite complex middlegames. It is not enough to know just the opening lines of the scandi, it also important to know these middlegames, and you will need strong endgame abilities to win (or draw) these positions - both as White and Black. This is the "problem" of the Scandinavian (and in all other openings I guess).
Wish you all best of luck playing both sides of the Scandiavian Defence.