In this post I will answer the original question, 'do USCF masters specialize in openings'.
Firstly, I recommend you read this book:
http://www.chessville.com/reviews/Build_Your_Chess_Opening_Repertoire.htm The short answer is that yes, nearly all USCF masters (ie anyone rated over 2200) specialize in openings. However, the extent and nature of this specialisation varies considerably.
Here are some varying levels and types of specialisation that masters exhibit:
Narrow and Deep This is what I would recommend to the majority of players aspiring to become a Master. With this repertoire, one plays only one first move as White and one (mainstream) defence to each of White's main first moves. For example, playing 1.e4 (Open Sicilian, Italian Game, Tarrasch French, Advance Caro-Kann) as White and playing the Scheviningen, Grunfeld and Symmetrical English as Black.
Although a 'narrow and deep' repertoire is easy for your opponents to prepare against, often your greater experience and understanding (this is the main advantage of specialization) will enable you to outplay the opponent in the middlegame, especially if they play a variation that is not one of the main variations in their opening repertoire. This disadvantage can be negated by specialising in several variations within your opening, e.g. playing both 6...h6 and 6...Nc6 against the Keres Attack.
Narrow and Shallow This is similar to 'Narrow and Deep', but with the difference that instead of specialising in mainstream openings, one specialises in less common openings with an inferior reputation. For example, playing 1.c4, 2.g3 exclusively as White and playing the Scandinavian, Budapest Gambit and 1.c4/1.Nf3 Nc6 as Black. The main advantage is that your opponent will usually be less familiar with the theory, making it easier for you to outplay the opponent.
However, the disadvantage (which for most masters outweighs this advantage) is that your opponents can prepare more specifically for these variations as they contain less theory, and as the surprise effect wears off, you are more and more likely to face a well-prepared opponent. In these instances, relying on your specialised knowledge and understanding may be insufficient as your opponent will be able to focus on this as well in their preparation, to a greater extent than if they were preparing for the Najdorf.
Somewhat Versatile and Deep This type of repertoire is my recommendation for the majority of players in the 2000-2400 range. It involves playing two first moves as White, with one being your main weapon, and another a sideline that one uses as a surprise weapon as a back-up. For example, usually playing 1.e4 but also playing 1.Nf3 as a backup, with the KIA (both via. 1.e4 and 1.Nf3) as a surprise weapon, and usually playing the Dragon/KID/Symmetrical English, but also playing the Modern, Chigorin and Reversed Sicilian as back-up openings.
This contains the advantages of combining specialisation with flexibility. The only two disadvantages of this are that there is more theory that one must learn and, especially at club level and below, there is a danger that playing a range of openings could lead to superficiality in understanding and therefore prevent a player from specialising in the middlegames arising from the opening. However, at higher levels this can be solved quite easily through hard work and playing plenty of tournaments.
Universal and Shallow This repertoire type can either work very well or backfire badly. It involves playing a wide range of openings with both colours, usually (but not always) openings which are not the most fashionable at present. For example, playing 1.e4, 1.d4 and 1.c4 as White (with a range of options within, e.g. playing both 1.d4 Nf6 2.c4 and 2.Nf3/3.Bg5), and playing the Winawer French, Classical Sicilian, Berlin Wall and Pirc against 1.e4.
Often this style involves playing to exploit your opponent's weaknesses, being willing to deviate slightly to force your opponent into variations they are uncomfortable facing. The risk is that the opponent may achieve a middlegame position they are more comfortable with and which you are unfamiliar with. This style works best for players who have time to prepare for their opponents and are adept in relatively uncharted territory, although I wouldn't recommend it until you are at least 2300.
Universal and Deep This repertoire type is the most flexible of all possible styles, but also requires the most work. It involves playing every single major chess opening, but with knowing the theory of each opening in enough depth to play them at a high level. For example, meeting 1.d4 Nf6 2.c4 with 2...g6, 2...e6, 2...c5, 2...d6 and 2...e5.
It is nearly impossible for a player to prepare for such a repertoire, but obviously it requires a huge amount of work and for the vast majority of players it is far better to focus on far more important aspects of chess.
At the moment, my repertoire as White and Black is a combination of 'universal and shallow' and 'universal and deep'.
Spend most of your time doing tactics and calculation (this includes analysing games).