A balance patch has just been issued for Super Smash Bros for Nintendo 3DS, bringing the game up to version 1.0.4. Nintendo has only given us quick descriptions of update changes in the past without going into detail on the finer fixes; as such, there's no proper changelog for v1.0.4. Thankfully, you can check out this reddit post to see what's different.
Various characters have had abilities buffed or nerfed. For example, Mario's Up Tilt does 5% damage instead of 6%, Ike's Fair is faster, Ness' Throw deals 7% down from 9%, and so on. For everyone, bomb cancelling and turnip cancelling have been fixed. There are many other changes, and the reddit list is constantly being edited as more are discovered.
These changes are most likely meant to bring the 3DS version up in line with the Wii U version that's launching this Friday, November 21. You'll be able to practice with the adjusted abilities for a few days before heading to the big screen.