I was digging up some 2013 web stats for someone else and came up with two quick stats that might be of interest to some:
Averaged over the year (2013), our digital exhibit and collection sites saw around 100 visits per hour, while our main web site saw around 280 visits per hour.
Or if you prefer, digitization sites saw ~2,400 visits/day, while the web site saw ~6700 visits per day.
No idea how this compares to other places, but good to know if only as a benchmark.