I'm not a counter; and I've not encountered too many Wongers in my play. But here are my feelings. I don't think they mess up the flow of the cards. That is just voodoo. They probably help as much as hurt in that respect, over the long term. I can't really complain about it too much, if the casino allows it. However, I have two problems with it:
1. Adding a player to the table uses up the good cards faster. IN that respect, if I have played a shoe up to the point where the good cards are about to come out, and then this guy jumps in and uses up some of those good cards, that isn't really fair to me.
2. I hate having to rearrange and tighten up the seating arrangement at the table, and go through the buy-in and welcome to the table slow-down bit, only to have the player jump back out after three hands. Yes, that is pretty rude.
As long as it isn't an all the time thing, the person isn't particularly over-bearing, or on their third trip into my table, I probably wouldn't say anything or do anything. I'd just grin and bear it. If, however, the situation got out of hand, I'd either say something to the player, complain to the pit, or find another place to play.