I think high tap solves one problem and creates three new ones in the process. You wind up putting more stress than you need to on the steppers, the reels, the kickers, and all the other parts that don't need extra power, and pretty soon things start breaking.
When the machines were new they could probably handle the additional stress since they were over-engineered to begin with. The trouble is, we're dealing with 50 and 60 year old machines with thousands and thousands of plays--it's like taking an old New York City Checker Cab and putting a new 454 V-8 engine in it. Sure, it goes faster, until the wheels fall off.
I've got one machine that came to me on high tap. Two pop bumper frames were cracked, both the 10,000 and 100,000 steppers had switches with blades snapped off, one had a broken bakelite linkage, and the machine had the worst coils I've ever seen with disintegrated coil stops, mushroomed plungers, you name it. I can't prove it was the high tapping that did it, but it sure looks like it to me.
At least with the high power flipper coils you're limiting the extra power to one assembly, but I don't want anything to do with high tapping an entire machine.