We used them for:
airport pickup to hotel
Bhaktapur hotel pick-up to Nagarkot hotel drop off
Nagarkot hotel pick-up to Thamel hotel drop off
They may be pricey when compared with taxi but I didn’t haggle with them. They had the highest level of communication, accept PayPal, and I felt the peace of mind was worth the higher costs. Before every pick-up I was sent photos of vehicle, driver, license plate, and driver phone number via WhatsApp. For those willing to pay for comfort and certainty I highly recommend Kathmandu Car Services.