Its been a mixed feeling about slabbing, but recently I have seen the pro surpassing the con. Example, I tried selling a book a while back on ebay with a reserve, unslabbed, and it did not sell. When I slabbed it,and tried re-selling it the reserve met in just 2 days. People are trusting CGC for the first and most important fact-- restoration. Anyone on ebay can say, the book is unrestored. I am not saying CGC is perfect, but its better than some joe telling anyone, the book is unrestored (when in fact he/or she is unsure themselves).
I even bought a GA book from a dealer once with a guarantee there was no restoration, when I slabbed it it came back (not too long ago) purple with a note of glue on the back middle of the spine. I did not even see it after checking it cover to cover. And I dont miss alot , but Im not perfect with detecting either. It could happen to anyone.