One thing that really surprised both of us was the number of hands where we both had at least one card that was the same. I'm gonna say that 90% of the time we got down to the river, we both had one card that was the same.

So can anyone calculate what the probability is of there being at least one same value hole card for both players? It's been 23 years since I had to do serious statistics so I've completely forgotten the methodology.