3 decks can be in play with the shuffletech if the bottom tray mode is utilized. One in play, one being shuffled, one already shuffled and waiting to be used. So zero wait time.
Although, you could have many decks in play with hand shuffling. If one were inclined, every player at the table could be shuffling their own deck.
But it's not really about speed with these shufflers. Although that is one definite benefit. It's really about getting a consistent decent shuffle every single hand. I've never been to a home game where 100% of the players are competent shufflers. There's always a few suspect folks. Old guy who is slow, someone with arthritis, guy with poor hand eye coordination, drunk guy who's now cross eyed and seeing double. Or the dreaded combo guy: old, arthritic, uncoordinated, and drunk.