I have a B&M console mega shifter in my 68 TH400, guy totally butchered the console up and it looks like crap.
I am in the process of getting the correct B&M trim plate for it and fiberglassing what damage was done. I then intend on putting a new NPD woodgrain kit over it.
As far as operation, I cant testify to seemless operation because it sometimes skips 3rd and goes right into neutral when shifting. It once went into reverse on me Luckily I was going slow. I think that that was caused by a lack of maintenance, , , I am looking into that too.
I would say though that if done properly and maintained it can look and work well.