this year like last year the union of taxi drivers hasnt set their final prices yet due to their demand for increase (petrol goes up).
a prebooked taxi from airport-hotel would cost around 55 per way (price can be a bit up or down based on the company).
with normal driving conditions is about 45 min drive.
the waiting in heraklion airport again depends on how many persons are looking for a taxi. i wouldnt say it will take you long as the drivers also want to get over with it asap in order to get other clients etc.
also in heraklion airport there is a board with the prices at the taxi station there, so as you will not pay more.

p.s. if late at night arrival then price change due to the hour of the day. if pre-booked taxi then the price CANT change regardless of the time of day

i would stick with the coach from experience, the greek drivers are terrible! costing will probably be expensive not sure where your destaination is in reference to the airport