Well, David Gearhart answered that question already:
Solidarity Mirror usually comes down to who has the most experience. The easiest thing to liken it to is a Mexican Standoff. The first guy to blink is the dead one, unless, the guy who blinks can support the blinkage. See? Kind of confusing. (If you don't know what a Mexican Standoff is.....for shame) By the way, the Solidarity mirror match will frequently take 1 1/2 to 3 hours.
I haven't been able to test the mirror alot, but I've tested Solidarity against Spring Tide (which is much easier). You basically wait until they cast their High Tide(s) and than you try to combo in response to one of their crucial spells.
I'm running two Twincasts in the Sideboard and have thought about bringing them in against the mirror (boarding out Resets). In this case, I would try to go off with one of their Resets on the stack, so I could Twincast it over and over again. I still have to test this, though.


One last thing I wanted to say: Peek is just nuts. I was running two Peeks in my deck at GP Lille and I absolutely loved them every time I saw them. They're great against Threshold, Control and the mirror...