I have my Metas with a Purifi amp. Detail is amazing. These can do a real disappearing act, but with a good sub or two they are truly amazing speakers. It’ll be interesting to see how they compare with the B&W 705s, Elac Vela 403, and the Monitor Gold 100s. I think at $1500 these are quite the bargain. 
The KEF dealer here is a rather low end store that mainly caters to home theater. The store doesn't have dedicated audio rooms so its a waste of time to try listening to anything in the store because of the ambient noise.

I have a pair of B&W CM5 S2 that are bright enough that I feel fatigue if I listen for an extended period of time.  Please will someone tell me what is the overall character of the LS50?  If I am looking for a speaker that isn't quite so bright is the LS50 something I should consider?

I use my non-meta LS50's with very neutral gear and have zero fatigue. I listen a lot of hours while I work.

The speakers will go into storage on Saturday to move in my new speakers, but I will never sell them, just love them. 
Yup no fatigue with old Ls 50s and not expecting any with the metas either based on limited audition and reviews to date.