Personally, I consider ivory ferules to be a liability in a playing cue. The higher deflection, maintenance and expense are things I can do without in a cue that I play with on a daily basis. Also, ivory is not as durable in the long term as synthetic materials. Granted there are probably lots of players that have been firing away with an ivory feruled shaft for years, but those I think are exceptional cases, rather than the norm.
Ivory joints are fine and I actually like them. I had a Barrenger cue with ivory ferules, joint and butt cap with a G10 pin. That was a phenomenal cue to shoot with and made my game better because it forced me to develop a smoother stroke. The feel of that thing was just awesome and I wish I saw more of Joes work.