as i've always said, i prefer buses to taxis. they will never go on a strange, longer route. they will never overcharge you. you only need lots of patience to wait for them to come.

just a few corrections:
1. the flat fate of QAR 10 is the price of a 24-hour 2-way/return ticket. that means it's QAR 5 per trip as long as you don't tap out when you get off the bus as the card reader will read that as your second trip
2. the fare can actually be as low as QAR 2.50 depending on the bus route you take and the distance you travel if you have the smartcard. you only need to tap out (as opposed to the ticket type in 1) when you get off the bus so it will charge you a certain amount depending on the distance you travelled in a particular route. some circular routes within doha (e.g. buses 57, 74 & 76---the ones going to city center) charge a flat fee of QAR 3 though.