If you've come across the biomechanical arguement in terms of free will, this is something to consider. Even if will is simply an execution of physics, the word 'simply' is not enough. If you trace the smoking gun of physics, it didn't start yesterday, nor the day before - it traces all the way back to what we currently understand as the larger origins of everything, the big bang.
Even if free will is simply physics, the final expression of physics that is free will is an expression that originates in a big and still pretty damn mysterious explosion! You could literally consider your own will as a small ongoing part of that explosion. Indeed if scienctific evidence forces you to think of youself as biomechanical, then your just as much forced to consider yourself as a small part of that explosion, ongoing.
Will we grasp the origins of that explosion more thoroughly in future? Probably, but its a much more grandiose thing. The frightening element of simply seeing oneself as a biomechanical machine is that it seems so pointless and meaningless. But that's basically because it's such a short term way of looking at things (if humans are very flawed, to look at it this way is to engage in another flaw). Beyond our ability to grasp from moment to moment, we trace all the way to one huge explosion that pretty much made everything (or atleast allowed it to exist/birthed it). That's pretty significant!
If you haven't run into the biomechanical arguement - in a way you both need to know, yet I'm lothe to say since I wont be there to run it past you in person. I'm not sure it should be passed on alone. Anyway, here's a long essay that might help on it - it's long, so maybe you wont get through it anyway, or find the length to be some company.
Also see: Philosophy: An arguement against "Humans are fundamentally bio-mechanical"