Provides liquidity, and typically earns a rebate or at least avoids paying the spread.
The trade-off: a better price, but no guarantee of execution. And the fills you do get are adversely selected - you fill when the market comes to you, which is disproportionately when it is about to keep going.
Where the risk hides. An unfilled limit order in a fast market means you did not get the trade you wanted, which is a real cost even though it never appears on a P&L statement.