VPIP = Voluntary Put Money In Pot
As the title says, what VPIP would you consider to be solid percentage/player?
I think if players play 20% or less hands in tournaments, they're usually pretty solid. Typically, the less hands you play the stronger hands you end up playing.
I agree that players with 20% VPIP or less will often have stronger starting ranges, but in tournaments I don't think low VPIP automatically means better or more profitable play.
A loose-aggressive maniac can be very dangerous in the right tournament situation. Someone playing 40%+ VPIP can put enormous pressure on the table, especially when they have position. On the button, for example, a very aggressive player may raise a huge percentage of hands when the blinds are tight or trying to survive.
Sometimes that aggression can even include 3-betting hands like 72o. Obviously, you can't just play every hand like that and expect to win — the point is that a LAG player is constantly putting opponents in difficult decisions and forcing them to defend their blinds and stacks.
The advantage of the loose-aggressive style in tournaments is pressure. You can accumulate chips without waiting for premium hands, attack players who are trying to ladder up, steal blinds and antes frequently, and make opponents uncomfortable enough that they start making mistakes.
A tight player may have a stronger average hand when they enter a pot, but a good LAG can often win many pots without showing down a hand.
So I would say VPIP tells you something about a player's style, but not necessarily how dangerous or profitable that player is. A 15% player can be predictable, while a skilled 40%+ LAG can be one of the toughest players at the table.