Well, here's my 2c.
1) I own some, and they're in service. Work well, look neat. 2) But, there is risk of marring the lovely embossing on the favorite GB, Cinelli, or Nitto bars. 3) Even if you get reduced to using radiator clamps for attachment, because the old hardware just wasn't that good. 4) But, better to mark the handlebars than scuff the paint mounting down-tube or seat-tube bottle carriers, eh? Particularly when access is so much better. 5) There's something eyecatching about an older bike in full kit, including the TA bottle with its sprinkler cap still in place. :-)