Can't directly comment on the product itself, but the support from Ohuhu is outstanding!
I purchased the product, but my shipment was onshipped and got caught by another shipper who refused to onship as they argued the product was a Dangerous Good (stupid as I've had other alcohol-based pens shipped by air freight). The shipper wouldn't budge even though Ohuhu helped, supplied an MSDS etc and did everything possible, which finally ended up them providing a full refund even though the issue wasn't their fault.
If they helped in this case, then I'm sure they would stand behind the product if any problems occurred. Their help desk was fast, helpful and went beyond expectations.