Meeeh. I guess I just prefer quarries due to the inherently low maintenance.
I used turtles early on, but I got away from them as early as I possibly could. I got tired of moving my ender chest every time my minecraft crashed.
I agree - I prefer quarries too, especially being able to run them at max speed off our boilers, but they're pretty hard to beat when you're just starting out and don't have the 11 diamonds needed for a quarry or any of the other ancillary equipment to power them. The other advantages of the turtle (austinKK's prog specifically) is that it starts from bedrock and mines upwards, so you get all the good stuff first, plus it doesn't care for lava or water in its way, unlike quarries.
Try one when you start your next brand new world, I think you'll be quite impressed.