What is a healthy memcached hit rate?

[Dani]

I have four memcached servers, 2 GB each. Each one averages about 1 set operation per second, and 500 get operations per second. However, the hit rate is incredibly low at only about 45%. Is this still efficient considering that, even taking into consideration only half of the get operations result in a successful retrieval, we're still talking about 1 set operation per second to 250 successful retrievals per second per server??