Thanks for the input.Mario's best damage dealer at low percents. It's an easy 25% on many characters (or even like 40% on fastfallers) by itself if you get it off at low percents (beware, at 0%, if your opponent is smart, they will shield the 2nd U-tilt, so instead of U-tilting there, do a D-throw to be safe).
U-tilt juggles set up perfectly into U-air juggles, and you can get off about 50% if you connect with a U-tilt juggle and two U-airs. The thing that is so great about U-tilt juggles is that even if you don't commit to just U-tilts, Mario is almost always able to mix up with something faster than his opponent can do other attacks.
U-tilt hits through BF platforms. U-tilt is good setup for jablocks on Luigi's Mansion. This move is the reason why characters need to be cautious of Mario at low percents, because one U-tilt at the right moment can carry them to 60% quickly.
I'm glad we have a longer explanation. I already have most of this down, but I'll quote this for justice.