Yes!  Though it is required by Washington State Law for a seller to disclose all what is wrong with a property, that they have knowledge of.   Often times Sellers are just as surprised about a discovery an inspector has made, as the Buyer.

This is your chance to kick the tires, so to speak, and it is a very important one.  The inspection, if written properly allows the buyer a short reasonable amount of time (usually a week to ten days) to have the property professionally inspected.  The last thing a new home owner wishes to do after purchasing a home is pay for a costly surprise repair.  Not only will an inspector get you the information so you can make an informed decision about the home, the inspection also affords you an opportunity to negotiate further concessions from a Seller, depending upon what is found.  Especially if it is something the seller will have to deal with when the next Buyer comes along, should you choose to back out of the transaction. 

So always have an inspection.