Here are some things that I think would make the world a much better place:
1) Thunderstorm sounds in public bathrooms.
The random thunder noises would cover up the random butt sounds for the poopers and the rain sound would help people with shy bladders. Everyone wins.
2) The new version of Windows would be new.
Start from scratch. Do it all brand new and dont worry about being legacy compliant. Apple has proven you can do both. Create an ultimate super stable and secure version of Windows from the ground up and if you want to run old Windows apps, you can do it virtually.
3) Allow me to own all of my personalization options.
I should have one password file, one wallet file, one bookmarks file, one of everything that I use and I should be able to use it on any system I get on. There would be no difference between my data on a cell phone or an ATM or anything else.
4) Make celery taste like bacon.
You can eat celery and burn more calories doing it then you take in and while it's yummy by itself it could be better. So they need to start doing some genetic engineering on it and get us some new flavors. Bacon flavor would be a good start. I can just imagine a crazy lab setup with a stalk of celery strapped to one table and some bacon strapped to another table with all these wires connecting the two thru some huge crazy machine with random blinky lights. Although in the wrong hands I guess you could end up with bacon that tastes like celery.