most people kinda took what i did at pound 2 to be unstoppable... but thats hardly the case. Its unstoppable in the sense that falco's dair shine is unstoppable. Meaning, its difficult to get around sometimes, but you hardly see anyone's sheild getting owned left and right. Not even shizwiz will be breaking sheilds with it.
For its effectiveness... the pressuring is mainly nair to double slap, oftentimes to slaps getting to them as they try to get away. The slaps send them in such a way that another nair can follow up in most cases. I've personally taking a couple peaches and like a marth or 2 across the stage with nothing but 4 or 5 nairs. Against peach its an actual combo at lower percents for at least 2 to 3 hits, anything past that is poor DI. Marth pretty much requires poor DI to get caught in that, but part of the effectiveness is flustering the opponent. But granted, against marth, nothing to rely on.
Against almost all but the floatiest, nairing the sheild into double slap gets them out of the sheild with slaps, and then as they try to save themselves again you work their sheild over again with a nair.
But of course, you can roll and sometimes grab. But since FC nair is so fast its not something the opponent will always be prepared to do.
Now the best part of FC nair is the mixups with grabs, single slaps, d smash, dash dancing away, etc. Its the options.
Now if you like the pillar because of the sheild owning opportunities, i'd look for something else. I've broken one sheild in the year i've been doing this fairly often in tournament. (A big ol =D, but for peach in general, D=)