I've heard some speakers with metal dome tweeters I like, but in general I don't get on with them because they tend to lend a bright, forward, nature to the sound. Silver plated (not solid silver) cables also give a similar effect to my ears.
However, as with anything else in hi-fi, it's not what is used but how well it's implemented that counts, so I would never automatically dismiss metal dome tweeters for that reason.
Marco.

