Alright, so I ordered the Canon 70-200 f/4 L non-IS. Actually two as I did not realize I couldn't cancel an order and I had a 20% coupon that I wanted to use. Anyways, so I get both lenses and inspected them. The outside is fine other than some dust I was able to blow off with my blower. Looking through both of them though they both have a pretty good amount of dust in them. I'm trying to decide whether it's worth paying to ship it Canon to have them take it apart and clean it or not. I was hoping one would be clean at least and I could keep that copy but they both have it. I've taken some shots and I'm not seeing anything. Perhaps I'll have to shoot at f/22 at MFD and see if I can see it. I asked lens rentals their thoughts and this is what I got back in reply:
Its hard to say what you might be seeing without a visual but it sounds like either dust or cleaning residue. Most used or refurbished lenses will have a light to moderate amount of internal dust. If they aren't very noticeable, chances are they will never affect your images. There is also a good chance that Canon has opened up the lenses to be repaired at some point and left residue on the elements from cleaning them. This is not ideal, but again will probably never affect image quality. If you are uncomfortable with what you are seeing I would bring it to Canon's attention with some photos of the spots on hand.
I wanted to get everyone's comments on what they thought I should do. Thanks.