From the comments I've seen they seem to be well regarded and in pictures look decent enough (I know - pictures can be deceptive). A demo video I found suggests that they do a good job of blocking wind but there's no way really to tell from the video whether they do it at the expense of killing too much HF.
If I could get hold of them I'd gladly buy a couple to try them against my Rycote Softies and Schoeps W20/W20S but it seems that they're not available in the UK. The purchase pages on the Micover website appear to be blocked from UK IPs and neither Amazon US nor the two other US based shops I tried would ship them to the UK. A pity really as, if they work as well as the Rycotes and don't trash the sound, they're a lot cheaper than the equivalent Rycote. Much as I love my Rycote and Schoeps fluffies, I only need to use them maybe half a dozen times a year and they tie up quite a lot of money for so little use. The price differential between those and the Micover Puffins certainly adds up when one needs more then just one or two and even if the Puffins are a bit less 'heavy duty', for the kind of work load I have for them they still might be worthwhile. If they hold up in terms of their construction, materials and function then they could be a bargain - in those countries where they're available. If not, then I could always stick some eyes on them and use them as luxury cat toys!
If someone that side of the pond fancied snagging a couple and sending them over here (I'm quite happy to pay for them and the shipping) I'd give them a go and see how they compare.