I can't say enough nice things about this thing.
It truly pulls off the look of a classic water bottle cage like nothing else on the market. It looks fantastic and it's timeless: It looks as good handlebar mounted on a '51 Raleigh 3-speed (with a Minoura adapter) as it does on the downtube of a backdated '82 Schwinn Superior, and it wouldn't look out of place at all on a modern carbon fiber wonderbike. In fact, I wish they had these in black/noir for some of my more modern rigs.
As for practicality, it also wins on all accounts here too. The neck/opening is about 74mm when at rest, and it'll fit just about any 73mm bottle without trouble - whether it's an aluminum or plastic sport bottle/thermos. The circular design without a tab means you're not restricted to modern sport bottles with reduced-diameter necks, so now you can put those 2,398 "swag bottles" you have lying around from useless conferences and meetings to work. Sure, it won't be as snug a fit, but you won't have to fight the thing to get a drink either; particularly important if you like your bottles handlebar mounted.
What's more, this cage will even hold a convenience-store water bottle - the thin plastic spring water kind. Not only will it fit the sport type (which usually run ~73mm and are a direct fit), but it is JUST tight enough to cradle a much smaller, 65mm 16.9oz bottle from flying out. That's something that no conventionally-designed cage (or even the Moderniste) can brag about. And hey, you never know when you'll wind up needing to carry one of those. I like that kind of versatility.
About the only thing you'll find is that aluminum 73mm bottles might clank around a wee bit in the cage, and may not be ideal if you're riding on gravel. I ride pavement, so it doesn't bother me. If you can't stand the rattle (or want a tighter fit), you can always dip the top in black Plastidip, or shove something in the gap as a short-term measure.