I am biased since I fly it (sometimes), but I will say that it is an excellent airplane for what it does. It was designed to be easy to operate, reliable, and efficient.
We have had plenty of pilots with no turboprop experience learn to be excellent captains on the ATR. The systems are quite automated, more so than the CRJ-200's. It is a challenge (like any airplane you are just learning) at first to learn how the system automation works, but it really cuts down on switch-flipping and really pilot-proofs the airplane (think Airbus here). It has heavy flight controls, but you've got enough control authority to do what you need to do. It is a very stable airplane, but less so when the flight attendants starting walking up and down the aisle. It lands like a rubber ball (bouncy) and takes a definite, positive side slip to land in a crosswind without side loading it. The combination of a narrow landing gear, large wingspan, high wing, and a large tail make it a real handful in a crosswind. In other words, you will learn to land it well in a crosswind or you will scare yourself a bit. Aileron placement during takeoff and the landing rollout is crucial in a crosswind, or else one of your main landing gears might get a bit light in the loafers. But, once you master one of the many techniques ATR pilots use, you can get some very nice landings out of her.
As far as reliability, alot of that depends on the age and the maintenance of the airplane. Older ones break more often, but knowledgeable mechanics can mitigate this.
It is a very efficient airplane optimized for regional flying. It burns about 1600 pounds per hour at about 265 KTAS (on average). It does seem underpowered, but this is because the airplane does not let you use more than about 80% of the total available horsepower during normal climb and normal cruise. This increases engine life greatly, since it keeps ITTs very far from engine limitations. The engines are amazingly simple to operate. The power levers spend most of their time in flight in a detent called the notch; the crew sets power by rotating a knob called the power management selector. The power levers usually only come back when it is time to reduce power in a descent.
The airplane gets a bit hot inside in the summer since the packs aren't exactly huge. Keeping the temperature reasonable in the summer months is an art among ATR pilots. Barring this, the cabin is very comfortable for a regional airliner, much more so than the CRJ's cabin.
Pilots here at Almaty Southern Aeroflot love the ATR (but not as much in the summer). I know I will miss it when it goes away.