I've never heard anyone disparage the Selmer Series 9. They didn't last long on the market, so perhaps they didn't sell particularly well, but everything I've heard about them is pretty standard high praise from those who love Selmers.
The Centered Tone does tend to get a lot of the glory these days, when talk of old Selmers comes up, but I've never heard anything bad about the Series 9.
I don't have any general overview of Selmers, though I play them, but here are few reviews of some vintage Selmer models.
I'd gladly add a Series 9 to my collection, if one came my way. I'd also love to add an R.I. and a Selmer Albert. I'm just a fan of these instruments across the board.