I don't worry about it.
My pack, a Gregory Day-and-a-half, was water-resistant but now is not. I don't see much difference from before, even living in about 60 inches of rain a year.
The water resistance was always thwarted by putting wet items back in the pack, leaking zippers, puddling at the bottom, etc. Anything not dunkable went into a waterproof bag early on.
The only real issue I have experienced is increased weight from wet gear -- not really a concern with a day pack.
I guess what I am saying is that, even with an uncoated pack, things only get so wet. And, regardless of how waterproof the pack is, the contents won't stay very dry if you use them.
Not worth the worry, IMHO. Get the pack you like.
Scott