So far I've found the fixed fares to be OK. Less than 1% loss on aggregate and, to be fair, they work very well in North County Dublin. Folk in these parts like to know what stuff costs before committing to buy it. Fact is, armed with that knowledge they will (and do) use more taxis. Also, there's a cultural hatred of taximeters among the older punters, the vast majority of whom have a horror story or ten to tell about non local drivers playing their meters like slot machines or something equally unpredictable. Of course, they don't think of extras for phoning for a cab or higher rates at different times of the day or week but if losing less than 1% off the total fares gives them some peace of mind that's okay with me. In reality, you'd probably lose a lot more rounding down anyway... which is something I never do on app payment jobs so there's an element of swings and roundabouts, I guess.
Don't forget the Dublin taximeter area was only extended nationwide to stop Dublin drivers taking the piss at peak times as the commuter belt extended beyond the traditional 10/15 mile radius of the GPO. I guess, to that extent, it works well as long as it's a maximum. I think any minimum metered fare should be restricted to traditional meter areas and governed by local authorities in consultation with local taxi drivers. One size doesn't necessarily fit all.
The problem, of course, is that Uber currently subsidises our wages by giving clients very substantial discounts financed out of it's own very deep pockets. As we have seen with Free Now that won't last forever so it's pretty certain that the fixed fare rates will be reduced and/or rates of commission will be significantly increased going forward. Things might (and do) work pretty well while there's loads of money around and while Uber are subsidising our wages to the tune of millions of euros every month but neither of those factors will last forever... bet then neither will any of us!