hmm ... ok, i received the 1.4x magnifer yesterday and experimented with it. i used it with my 50mm and 80mm, as well as my 28mm. a few impressions ...
first, you can easily see the 50mm framelines. (i have read that you can barely make these out, but i am utterly confused by this comment.) in fact, i could make out almost all of the 28mm framelines.
second, the view is somewhat dimmer, with lower contrast. (this has been mentioned before on RFF.)
third, while it provides an improvement in focus, i found the advance to be mild. (it seems to be better with the enlarged focus area, but worse in regards to being dimmer and having less contrast.) i guess the benefits may vary for people with different types of vision. the -.05 improvement given by the normal M8 viewfinder fits well with my vision. thus, normally, i don't have great problems with focus. with the 1.4x magnifier, focusing was easier, but not markedly so. (in addition, i can see the small advance in focus being helpful to someone using the nocti, but it didn't seem necessary in my use of the lux.)
thus ... i will be returning the 1.4x magnifer. i'm not saying that it's not good; i'm saying that it's not necessary for me. as mentioned in a previous post, i'm a champion of the streamlining of gear. i don't want another item unless it bares a significant overall benefit. and, for me, the 1.4x magnifer does not do so.
saying that, i remain somewhat interested in trying the leica 1.25x magnifer. having used the 1.4x, i know the 1.25x would work with my 28, 50 and 80--and i have read that it is significantly brighter than the 1.4x. however, trying the 1.25x magnifer is not a current option, as it's backordered at all normal leica sellers. (and i would want to use the leica magnifier, not one of a competitor.) but, when it becomes available, i could see myself testing it ... to verity that it can be used on the three aforementioned lenses--and to see if it permits enhanced focus (versus the use of no magnifer) and is brighter than the 1.4x.