I have Be-20 with the original tweeter and last year got the new DMD tweeter installed.
First I have to say that I could not have care less about beryllium tweeter being beryllium/titanium tweeter. I bought the original speakers because I like what I heard and at that price point, I could not find anything locally that I prefer over Be-20. When it came to light that the tweeter is not pure beryllium, that certainly did not make my speakers performed any worse than when I thought it was pure beryllium.
Then I had a chance to hear Usher with new DMD tweeter and I did not hesitate to have the tweeters changed at all. As good as the original tweeters were, the DMD tweeter is smoother, richer sounding without losing any detail. Not that the old tweeter was thin sounding, the new tweeters just improved upon the older tweeters significantly IMHO.