Cydia 1.1.20 is a bug fix release
Section Hiding Sometimes Crashed
If you went to "Sources", tapped "All Sources" (or an individual source), tapped "Edit", and toggled section hiding on or off, Cydia could crash. (This feature lets you hide specific categories of packages from showing up in "Changes" if you aren't interested in them.) Cydia should no longer crash when you do that.
Ignore Upgrades Didn't Do Anything
If you had gone to "Change Package Settings" at the top of a package page for an installed package, and then chose "Ignore Upgrades" (which means "do not include this package when selecting Upgrade All"), that feature wasn't doing anything. It should now work again.
"Fix Half-Installed Package"... Didn't
Ordinarily when a package installation fails for some reason, it can be left in a "half-installed" state, and Cydia offers to fix this state for you — but this wasn't working. Now if you get a half-installed package and accept the option to fix it, it should get fixed.
Storage Reported Impossible Values
If you went to the Cydia homepage, tapped "Storage Information", and tapped "Storage" to learn how much room you have for new packages, Cydia reported strange numbers. Cydia should report reasonable numbers now.
Missing Changelog Item Re Backup
When we wrote the changelog for Cydia 1.1.19, we forgot to mention that as of Cydia 1.1.19, your sources list is now included in your iTunes backup. This means that if you add a few sources, backup your jailbroken device, restore, and both put your backup onto your device and jailbreak again, Cydia will conveniently have your list of sources including the ones you added.