A Collaberation hack made by me and my pal Kosmicd12. It features plenty of custom music and some graphics. It also includes the "high jump" from Super Mario Bros. 2 (US). This is our first hack; Regardless, It's pretty good :) Have fun!
As for the hack itself, it has a good sense as to what the levels and their difficulty should be like for the early game, so it's mostly fair overall.
Aside from the music, there were only a few flaws to point out.
The banzai bills were too fast. It is true that they only appear in one level, and there are warning signs to indicate that they will appear, so the authors are being fair about it. However, anyone playing this hack blind will probably get hit at least once by the first Banzai bill. At least there are a fair amount of power-ups, and once they see one, they'll be more careful around the warning signs.
The high jump had an unnecessarily tricky control scheme, mainly when you had to hold an item at the same time. Follow me on this one. You hold the run button to pick up an item. You press and hold down to duck. Once you flash, you release down, then quickly press and hold the spin jump button a half second after you release down. It has to be exact, or you just do a normal jump.
I'd maybe even vouch to put this hack back on the site; of course the music has to be fixed first.