I think it's handy to understand if you have the time and inclination, but for the most part you don't need to know it in detail - just knowing that they are beneficial is probably sufficient.  Having said that, it's another tool to use in performance tuning and I have occasionally made queries run faster due to that knowledge.  If you just want to get your toes wet, knowing when statistics become out of date is useful. 

Here's a document I found:

http://www.microsoft.com/technet/prodtechnol/sql/2005/qrystats.mspx