I'm doing the quest Crazy, Crazy, Crazy.
I've met Neil near the top of the mountain, but when he asks me if I'm ready to go and I say something like "yes, let's do it" he gives me the response that he gives when I say Wait, "alright, hurry up then" (or whatever he says).
In short, I can't progress since he won't come with me.

I have also gotten this bug. Both dialogue options cause him to wait instead of proceed.

Ditto I just received this bug. I thought it might have been the 2 other companions I had but after dismissing the other 2 companions, Neil still won't join me regardless of what I say. He just stands there saying that I need to do what I need to do.

I re-loaded the game and dismissed my 2 companions before even talking to Neil at the summit as well and got the same message. Oh well. I just have to go further without him as an NPC.

Same here .. any fixs? u guys still have this happening ?

The 'fix' I had was just to go ahead and fix (ie kill) the Tabitha problem, then come back and talk to him still standing there.