I am not sure 4.Nc3 is the only move to fear.  I think the line 4.d4 fxe4 5.Nxe5 Nxe5 6.dxe5 c6 7.Nc3 (I assume this is what Craig was referring to?) is quite interesting.

Having said that, I think 4.Nc3 is probably best.  After 4...fxe4 5.Nxe4, it may eb that 5...Nf6 is objectively best, but 5...d5 probably puts more onus on White to know what he is doing ...

Thought it might be interesting to get some debate going on this line, which has been mentioned elsewhere. Do people think this is as good as any other line for black? Or can white get a large advantage by force? Do people prefer to play quietly with things like 4.d3, or play 4.d4 and offer a piece sac to rip the position apart? 

To get the ball rolling, let's consider the main line 1.e4 e5 2.Nf3 Nc6 3.Bb5 f5 4.Nc3 fxe4 5.Nxe4. Which do people consider stronger, 5...Nf6 or 5...d5? If 5...d5, does anyone have some improvements, since this line has had a poor reputation as of late? I have found in a correspondence game that even 10.Nxa7+, long considered to be harmless, gives white material and black not necessarily enough of an attack to compensate.

Regards, 
Craig