It's not so long ago that Uber was the new kid on the block, the shiny, disruptive upstart which was ruffling feathers and frightening the established player.
But now the San Francisco-headquartered company is facing a threat to its own hegemony, thanks to a string of legal judgements and negative headlines.
Uber is already banned in York and Sheffield, and it will lose its licence in London if its current appeal fails. The latest judgement from the European Court of Justice, that Uber is a taxi firm (rather than a third-party facilitator, as it had claimed) will only make things harder for the company and add grist to the mill of its detractors.
The same concerns remain: that Uber's perceived lack of self-regulation can expose passengers to the risk of sexual assault and other crimes, and that its drivers do not receive appropriate benefits and compensation. At present, the company is finding it fiendishly difficult to shrug off such concerns.
And, just as Uber iself once did, a string of companies are lining up to take a swing at the established player and bite off a big chunk of its market share.
Here are some of the rivals which pose the greatest threat to Uber's dominance.
Claiming to be Europe's fastest-growing ride-sharing app, Taxify already had 4,000 registered drivers and is expanding into all corners of the world, from Ghana to Australia.
The company, founded in Estonia in 2013, rose a reported €2 million in seed funding and has grown ever sense, to the extent that it now operates in 20 countries.
Taxify stresses the importance of customer safety, with all drivers obliged to pass a a criminal background check and in-person training. Although it lost its London licence just days after launching in the city, it is now planning a big relaunch.
This Europe-wide taxi hailing app has the advantage of operating in London, and customers can use cash or online payments - which is likely to be a bonus to those who want to split the fare.
It works for both iPhone and Android and, just like Uber, users can see their car's location is on a live map. It also allows them to make a phone call to the driver they've been booked with and the driver will wait for the user for two-and a-half minutes before charging, which seems like a bit of a bonus.
Just like Uber, MyTaxi is using discounts to build its customer base, and giving customers £10 off their first journey.
However the taxi that will turn up if you use MyTaxi will still be a black cab and whilst that's fantastic for those working in the industry, some may still prefer to avoid the meter.
Another black cab service based in London, Gett claims its cars arrive 3 minutes faster than Uber - something which sounds quite difficult to prove, although, if true, it'll make a big difference to stressed capital commuters.
You can pre-book the service up to two weeks in advance - less than Uber's 30 days - or request a taxi as you need one. You can even put a special request in for the driver and it allows users to pay with either cash or card too.
Rather than offering users only money off their first journey, users that refer friends can gain free credit of £10 and the friend will gain this credit too, so even though it's still sending black cabs, perhaps it could work out cheaper than Uber after all.
Admittedly, this is a premium London service (and it's long-established), howe that's not to say that it doesn't give a similar offering to Uber. Standard cars are luxury vehicles, but let's not forget Uber also introduced an option for users to travel in luxury cars too.
Customers can book cars up to three months in advance or request them at the time and they can also pay with cash, card or an Addison Lee Priority account. The cars are also equipped with 4G wifi and phone chargers. It's not a particularly new company, but the firm is planning to ride the technology wave, having earlier this month unveiled plans for driverless cars.
Addison Lee has had its own controversies - in September an employment tribunal test case found that some drivers had been wrongly classified as self-employed - but, given Uber's own issues, the firm will now see an opportunity to capitalise.