I haven't tried the Vivaldis yet, but I recently gave the Marchio Bleu set a whirl. I think they're a perfectly adequate string. They wouldn't suit all instruments, just as the popular brands don't suit all instruments, but if you're partial to a brighter sound or your instrument is a bit too dark, I think these strings would be a good candidate. They take a couple of days to fully settle in, as do most, but once they have, I find them quite pleasant under the ear. I haven't heard them from a distance, but I have no reason to believe they wouldn't perform suitably. I don't really understand how a person can make the immediate assumption that a set of strings are poor after experiencing them on one instrument. Granted, I know many only require strings for one instrument, but I wouldn't close a door on a brand just because one set didn't suit one instrument. I might try 5 different sets before deciding on the most suitable pairing. The resulting set may include more than one brand, depending on the instrument's requirements. I think some people can get locked on to the tone qualities of their favourites. Different is often good.
Incidentally, I was sent two sets as samplers. I saw an ad in The Strad and sent them off an email. I'm always keen to try new products. Maybe they're just trying to get their hands on the Australian market. Whatever the case, they were freebies. Mind you, I can also potentially buy quite a few sets and I'd imagine they take this into consideration when deciding who to send samples to. I think that's totally fair enough - especially for a small company. I agree - freebies are an essential component of marketing products like these, but you can't give every member of the general public who requests them a free set. That would be silly. I can also guarantee that the bigger brands have far greater profit margins than Dogal. Their capacity to absorb the cost of free samples would be far greater and they've likely budgeted for it and built the cost of the practice into their margins. That Dogal is a small family business in Venice, manufacturing strings by hand, is very appealing. I'd imagine the bigger brands started out in a similar fashion. Who knows - Dogal could be a dominant force in 10 year's time. I'm always happy to give the smaller guys my business, even if it means paying a bit more. Naturally, as a business grows, so too do the resources to improve upon the existing product.