Being unable to book a taxi in advance…
Being unable to book a taxi in advance means you're gambling. Like missing the flight if there's no driver available in some early hour. The other issue is app itself. As a first time user I accidentaly booked a taxy twice for there is no final decisive step like Proceed or Continue etc. Canceled at the last second. But I must say that when I did manage to get a taxi the expirience was really nice. Payed the exact amount as scheduled.