I recently had lunch at Onyx and it was a rather mediocre experience. While there was nothing specifically wrong, there were several things the venue could have done better.
First was the service. While I accept that people have bad days, the server was brusque and offered the kind of service more at home at a milk bar than a cafe.
Directions and service were abrupt and things I would consider standard (a glass for a bottled drink) was either unavailable or not offered. For a cafe with table service, one should not have to procure their own drink.
Non-alcoholic drinks were available in a self-serve fridge beside the counter, alcohol was visible and there was a coffee machine, but there was no drinks menu or any indication of offerings or prices.
The menu is limited (no issue with this) and desserts are again visible, but without prices or a menu (perhaps this was an omission on our server's part).
The food was average - the sandwich bread was so hard it hurt the roof of my mouth, but acceptable and the food was served quickly.
I'm not sure whether toilets are available, but certainly another patron was directed to the public facilities down the road.
Overall, it was average. There was nothing specifically amiss, but many things that could be improved upon - a full menu with prices being the most immediate. There are better options in Swansea and I would certainly be availing myself of them and not Onyx.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.