Buffs and nerfs as much as this time around? I'm going to say no.
The biggest things that come to mine are Bowser's updates saying something to the effect of "If you think Bowser is going to be the same as before, then you have another thing coming." Also he mentioned Bowser Bomb hits on the way up as well as down.
With Donkey Kong he explained how there was super armer on his big Gorilla Punch.
There are a few others as well, including outside of the Dojo he said on multiple occasions the theme of the game is on balance. I laugh when I think about it considering the final product. So while I do have a lot of hope for better balance this time around I'm not 100% convinced.
During Melee's development, Sakurai and Miyamoto talked about how Kirby was way too overpowered in 64 and was toned down and boy did they tone him down. Now though we haven't gotten word on anything being toned down(Aside from possibly Pit's Wings of Icarus), but instead things are being buffed up. Lucario, Donkey Kong, Link and Samus, these are clear examples of the buff happy nature Sakurai seems to be going through to make characters feel better and possibly hold their own with an extremely varied cast of characters. During the Brawl dojo I can't remember one update that talked about how much more powerful something or someone has become in the latest title. It really does seem like everyone will have something worthwhile that will allow them to keep up.