I finally got around to playing story mode some more and finished it off 100%.
This page is useful for figuring out all you need to do (I was missing the 2nd and 3rd stages the bird gives when I thought I was done).
How to unlock Mii costumes, find characters and collect coin
www.nintendolife.com
No real reason to do it once you've gotten the super ball unless you want the Mii costumes and to just have the satisfaction of completing it and getting the "All Levels Completed as Mario” banner to pop up.
The most annoying part was having to grind coins to keep paying the Chief 1,000 coins for each step (ten in total I think)to finish the statue and get the last job from Peach. That last level was pretty cool though. From the best coin farming levels I saw listed online, I found level 55 (the car one) to be the easiest. Pretty quick 117 coins a run once you get it down (which is pretty easy, once you figure out how to get the 50 coin).
Looking forward to spending more time playing user levels. Will check out the ones in this thread. I played a few last week, but I see a lot more have been added since.