I've had no dealings with them, but there are many, many who have. Some have complaints, the vast majority seem happy. I did a lot of looking when this topic was posted and couldn't find many cohesive complaints. Lots of warnings from folks who have never dealt with them, but not too many complaints from actual customers. Didn't find any posts about fake filters, either, although fakes can be very good.
As for them not being an authorized B+W retailer, that doesn't mean much. Grey market goods are always cheaper than authorized imports. I don't know what the mark-up is for photo filters but, as with all accessories, I'm sure it's excessive.
Not sure what your filter is going for from B&H as opposed to MaxSaver, but if the purchase price is, for you, affordable it might be worth the risk. Personally, I'm not sure I'd go for it without seeing, firsthand, the quality of product they're selling.
Still, it might be nice for the rest of us if you buy a few filters and let us know how it went