It really depends on how lucky you feel and what your tolerance is for a missed flight. And how much you hate cooling your heels in the airport for several hours.

The east coast sometimes has thunderstorms that mess up an entire day's worth of flights to Europe. I have been caught in this a couple of times over the years.

This year I am flying to Europe from the west, and I had a choice between 50 minutes and > 3 hours connection in Denver. I chose 3 hours.