I'm not a huge fan of the signature series but I guess it depends on the artists. It's so fricking easy to get a lot of artists signatures that they're not even close to rare. Eastman and Laird have signed so much stuff it's crazy to even try and count it.
I guess my problem with signed comic books having a 9.8 rating is that eventually, the ink from the signatures starts to permeate through the book and starts staining the pages behind it. I have a Detective Comics book signed by Bob Kane in black marker just like the books above. After 10 years, I opened the front cover and noticed that the ink stained several of the pages below it in a large, spot like, manner.
I know signed books aren't collected for their condition of the comic itself but when CGC puts a NM rating on it, that book won't be near mint in another 10 years, even inside that case but the 9.8 books without the signatures, will be in fact in better shape so hence is my problem with signature books. I feel like my TMNT CGC 9.8 books will be in fact better condition than the signatures series which I'd rather have a book that is in the best possible condition than to have an artist's signature on it which isn't even that rare. I'm sure I'm in the minority but it's just my opinion.
With that said, i'd still like to get at least one signature series book (to go along with my pristine CGC 9.8 already of the same book) of the major artists like Stan Lee and such.
My 2 cents here. Not like it matters.