I’ve never used them myself but there has been a few posts on them before (try doing a search). Sounds like there a good idea if you’ve got a really nice frame that your attached to and want to fix. Don’t think anyone has had any troubles running them fixed but I’d stay well clear of the new ones that have the splined interface for the cog.
Great quality hubs that can be easily converted between eccentric and straight axle. Different sized axle ends available to match your frame spacing. Standard sized bearings that are cheap and easily available.