Really nothing. Maybe if you intend to do serious off-roading you should consider full struts. They say the pucks can damage the control arms if they are too big...but if it's 2.5" or less it's not an issue (I went with 2" spacers just to be sure). Of the people who have leveled trucks, probably at least half are running spacers and have no issues.
I own the only Ram suspension shop on the east coast. Believe me when I say spacers are a cheap way to level your truck. But they will cost more money and aggravation later when they wipe out other components. You also loose the opposite down travel. So if you go up 2” you loose 2” of down travel.
Spacers on a solid axle truck are not horrible but an ifs truck like our 1500’s pucks are NOT OK ever.
If you click on the search bar for spacers you will find a weeks worth of good reading on the topic. We are here to educate and help each other. That’s what forums are for