No, I won't give you any reasons for jailbreaking your iPhone, but if you take a look at the apps being rejected by Apple's App Store, that's only the beginning. Another problem is that, for a software producer, getting into the App Store is becoming harder with each day, and it also takes a lot of time until your apps get approved.
These being said, and considering the fact there are a lot of jailbroken iPhones out there, having awesome apps for these "outlaws" is a reality. A cruel reality for Apple, I must add.
According to the official Icy page, this is a "take on the freeware package manager that uses APT repositories to install and remove packages available in another free iPhone installer application, Cydia. The goal was to create a fast, lightweight and more slick solution that is easy and cool to use. Icy is only at version 1.0, but we're already working on the improvements."
Built on Open Source Foundation, Icy comes with a slick interface, it only takes 1Mb on your device, compared to the 32 taken up by Cydia, and was design to work by eating only a fraction of your network traffic. Even more, Icy is following the trend set by Apple in the 3.0 firmware, currently still in Beta stage, and allows you to browse installed packages in landscape mode.
These being said, here's what to do if Cydia is not working at all, or stopped working - be sure your iPhone is still functional, and install Icy! Pretty cool, don't you agree? ;)