opening repertoire

+1!

It's simple.  The London System is such an easy opening to defend and draw against.  White is, in essence, offering a draw by move 3.  Why play chess if you are going to offer a draw (virtually, not literally) on the 3rd move?

With the London System, White gets no attack.  White gets no positional advantage.  White gets NOTHING!  NADA!  ZILCH!

The fact that you can beat some lowly 1700 player in an Over The Board game with minimum time control of Game in 2 hours, or the fact that you can win some meaningless 5-minute game online against any rating, is not a valid argument to say that the London System is "The Almighty Opening That Gives White an Advantage".

If you use a LEGITIMATE Database, such as the one on the New In Chess Website, which has over 1.6 million games, and you compare the London System vs KID complex (1.d4 Nf6 2.Nf3 g6 3.Bf4 Bg7) to Larsen's Opening (1.b3), read it and weep.  Even 1.b3 scores better for White!

1.d4 Nf6 2.Nf3 g6 3.Bf4 Bg7 - 5404 Games, White wins 1826, Black wins 1906, 1671 draws, White scores 49.2%

1.b3 - 5065 games, White wins 1878, Black wins 1833, 1353 draws, White scores 50.4%

50.4% is still not good for White, but it sure beats the Lowly London of 49.2% by over a full percent!

So be happy your opponent is giving up their advantage then?

In essence, yes!  Against a lower rated player, you should be able to simply beat by playing chess.  Against higher players, take the easy draw and be happy.  Don't press too hard.

That said, I get lower rated players at the club occasionally asking me about their games, and wondering where they went wrong.  If they are White, and it's a London System, I tell them move 3, and refuse to go forward.  That's what little respect I have for the London.  I'll analyze a Colle-Koltanowski, Colle-Zukertort, Torre, Trompowsky, Veresov, or Blackmar-Diemer with them, even though we all know 2.c4 is stronger, but not the London!

Even I have played the Colle (twice), Torre (maybe 2 or 3 times), Tromp (a handful of times), Veresov (at least 50 times), and the Blackmar-Diemer (well, never exactly, but an offshoot of it once in the French), in my over 2000 games, but the London still is, and will always remain, at ZERO as long as I have White!

To my shame, I have to admit that I actually have no idea what the London System is.

In my games you'll find Frankenstein-Draculas, Hillbilly attacks and stuff like that. It just SOUNDS like more fun....

I'm around 1600 ELO and my openings are as follows

White: 
Vienna game 
Smith morra gambit against The Sicilian 
Birds opening is my surprise weapon

Black: 
French (for e4) 
Dutch (for d4)  
St. George (baker defense) (a6) is my surprise weapon
(against English I don't really know what I do, I never face it) 

I'm not going to be a Grand Master and I know that, these are just my way of playing. Its a fun and the surprise weapons work well and I have had numerous people sitting 20 mins after e4 - a6. They are stunned and don't know what to do. 

rooperi, the London System is 1.d4, 2.Nf3, and 3.Bf4 against 1...d5 or 1...Nf6.  It can be played against the Nimzo-Indian/Queen's Indian setup, King's Indian/Grunfeld setup, or double Queen Pawn openings.

QuiZi - You are like me.  A main opening and a surprise weapon.  However, for me, I'm on the other side of the spectrum.

White:  1.d4
Surprise Weapon:  1.g3

Black:  Modern against 1.e4 and 1.d4
I also play 1...e5, but looking to change that to 1...d6 with intentions of Nf6 and c6 against 1.e4 and 2...e5 against 1.d4 and 2.c4.

Like 1...g6, 1...d6 is also playable against most first moves by White.  1...g6 tends to be more tactical, 1...d6 more positional, so once I know both, I'll mostly play 1...g6 when playing away from the club, and at the club, it would depend on who I'm facing.  1...d6 against the tacticans, 1...g6 against the positional gurus.

I also play 1...g6 and 1...d6. You have a very cool repertoire. Right now, Because of my very LIMITED time, I'm sticking to 1.b4 as white and 1...b6 for the Black pieces. Against white's 1.g3, I'll go for 1...d6