You will no doubt get varied opinions but herewith my own thoughts, for what worth ....

- a high quality facility overall, very spacious & well-designed
- a welcome benefit on ULH flights (eg MEL-DXB, 14+ hours)
- for short or mid haul sectors, more of a novelty factor really

Would just add - given your reference to BA - that it's perhaps just as well BA don't offer onboard showers : I would be very sceptical as to their ability to actually keep them clean, amidst their declining standards where attention to detail is concerned. My own experience of the EK showers is that they are maintained to immaculate standards throughout the flight and credit for that must go to the conscientious shower attendants (two on each flight, assuming still the case).

Not sure that there is any justification for Emirates to use the word 'spa', as they do in their promo material, but that apart, it's worth a try so definitely give it a go, I say. Don't think you'll be disappointed - especially if you're fresh from BA !