I've been listening to pair of LS50 Meta's the past few days. I am very impressed with these speakers. Are they the most accurate, detailed, or full range speakers? Nope. Are they extremely engaging and fun to listen to? YES! There is an energy in the upper frequencies that is very "live" sounding that the originals lacked. They weren't bad, but these are at another level. They have amazing imaging, which I think is KEF's calling card, and these don't dissapoint. Great depth and space. I'm using a pair of REL T5i's for bass and I haven't turned them off to listen to LS50's on their own, but I'm getting a large dynamic sound that is close to whatever floor standers I've had in my room. The first evening I listened to these I did hear a flattening or slight smearing in the upper midrange, but haven't heard it as much since so maybe some break-in helped.The rest of my system is:

Odyssey Kismet amp
Don Sachs latest preamp
PS Audio DS Jr. DAC
REL T5i subs

This weekend I'm going to bring my other my Clearwave Duet 6 monitors back out and compare. The Duet's use Accuton ceramic drivers and high end crossover components and retail for double the cost of the LS50m's. I think they are certainly more accurate and detailed, but right now I couldn't say they are more fun to listen to. We'll see...
I also tried my new LS50 Meta's this week.  They seem to be a distinct improvement over the LS50, with better clarity and sound stage.  I use them with duel REL T/7i subwoofers.  They seem to need more amp power than the LS50. I have a Parasound Halo A 21+ with Paraound P6 preamp.  They also seem to improve markedly with break-in.  I would apprecieate any comments on my observations.  Thanks.
I commented in another section of the form. Compared to my old ls50, the meta’s are clearer, and seem to have a wider soundstage. Before breakin, I had to turn the metas up louder  than the old 50’s. However the meta’s play louder then my old 50’s at the same volume level. Bass is cleaner and blends with my sub better. The first thing I notice on first playing the metas was the transparency. I hear things is some recordings that I did not know insisted. It good to point out , that the transparency does not come from brightness. I am using mine with a pass lab integrated so my metas have a nice warm midrange. This was true with my old ls50 but now everything is much clearer. 
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?