Yup, pushers get in the way of the incoming air flow. If they're designed to be there they can work, but, if you just slap them on in front of a mechanical fan set up they usually do more harm than good because the mechanical fan wants as much uninterrupted air flow as it can get and the pushers sit right in the middle of that. They can work, but combining them with a mechanical system isn't an efficient way to do things.
As far as electric fans in general, you just have to take the time to figure out your new system. The CFM capability of the fans has to be matched to the cooling capacity of the radiator and the horsepower the car is producing. Then you have to make sure your electrical system can handle the draw that the correct CFM fan will pull. And then you need to control the fans properly so they're running when they need to be. Pretty much all new cars come with electric fans, and they're all designed to go well over a 100k miles. Properly set up, electric fans can work great. I love the Ford Contour electric fan set up I run on my Duster. It pulls a crap load of air, has a shroud that fits my 26" radiator well, and because its a factory part I can get parts for it anywhere. And the fan itself was only a little over a 100 bucks because it's re-popped, so, it was MUCH less expensive than some of the fancy aftermarket electric fans out there. But, I also spent money on a digital controller, upgraded to a 100 amp alternator, and set up a relay system off of a continuous duty relay to power it. That's where most folks go wrong, if you just slap an electric fan on there without a shroud, run it off a simple thermostatic switch and scab it into the stock electrical system your results will probably be underwhelming.
Mechanical fans can have failures too, and although they're generally more reliable when you have a fan clutch or blade failure (riveted blades) the results can be catastrophic. But, they fail less frequently and have a lot fewer parts to fail. If you have the space and the factory system works its a much easier way to go. Make sure you've got the right fan shroud and a good fan and clutch system and they're pretty darn good. But do to space constraints and application they don't always work for everybody.