Due to a discussion in another thread I open this to enter a discussion about the state of the art of this line.
First some Material : A useful site for entering the topic is this one: http://home.pacific.net.au/~davidflude/varaaa.htm

I'll add some analysis to 6...c5 and 6..e5 later on, Just some impressions now:
- accepting the gambit (6...exf3) IMHO more or less automatically leads to a win for white.
- 6...e5 is fairly interesting
- 6...c5, the main line requires a lot of theoretical knowledge from both sides.

Both replies for black mentioned above are playable, none of them deserves a "!", 6...e5 may deserve a "!?"

Starting with 6...c5, for answering NMB's question for this game:

[Event "WRG2-2 theme corr"]
[Site "SEMI corr"]
[Date "2000.07.15"]
[Round "0"]
[White "Flude,David A"]
[Black "Everett,Brian S"]
[Result "1/2"]
[Eco "C15"]
1.e4 e6 2.d4 d5 3.Nc3 Bb4 4.a3 Bxc3+ 5.bxc3 dxe4 6.f3 c5 7.Rb1 Nf6 8.Bb5+ Bd7 
9.Qe2 cxd4 10.fxe4 Nc6 11.Nf3 dxc3 12.0-0 Qc7 13.e5 Nd5 14.Ng5 Qxe5 15.Qxe5 Nxe5 16.Bxd7+ Nxd7 
17.Rxb7 N7f6 18.Nxf7 0-0 19.Ng5 e5 20.Rb5 Rab8 21.Ra5 h6 22.Nf3 e4 23.Nd4 Rb7 24.Rc5 Rc7 
1/2

Well... this subline (7.Rb1) may be interesting, but not at all critical, neither for white nor for black. 
For this special game, IMHO a bit "thin" as a reference game
If you do not like this kind of positions, try 7.Nh3, there's a lot to investigate.

[Event "WRG2-2 theme corr"]
[Site "SEMI corr"]
[Date "2000.07.15"]
[Round "0"]
[White "Flude,David A"]
[Black "Viola,Matteo"]
[Result "0-1"]
[Eco "C15"]
1.e4 e6 2.d4 d5 3.Nc3 Bb4 4.a3 Bxc3+ 5.bxc3 dxe4 6.f3 c5 7.Nh3 Nf6 8.Nf2 Nc6 
9.fxe4 cxd4 10.Bd3 Qa5 11.0-0 Qxc3 12.Rb1 Qc5 13.Rb5 Qf8 14.Bf4 e5 15.Rxe5+ Nxe5 16.Bxe5 Bd7 
17.Qc1 Qe7 18.Bxd4 0-0 19.Qe3 Qe6 20.h3 Bc6 21.Qg5 h6 22.Qg3 Nh5 23.Qf3 Qd6 24.c3 Ng3 
25.Re1 f5 26.Qe3 Qg6 27.Bc5 Rfe8 28.e5 b6 29.Bb4 Rad8 0-1

I'll comment on both games later on ...