The Carthorse and the Stallion
My iPhone has always been jailbroken. Since Day One.
At first, it was one way to unlock it since it was only available in the United States, and required to be activated through AT&T.
Then it became much more. Many indy developers seized the opportunity to create tweaks and distribute them through Installer or Cydia. These tweaks allowed me to do much more with my iPhone, or do things more easily. However, many were badly coded, or not thoroughly tested, thus bloating the phone and leaking its battery.
That is the carthorse: useful but slow.
But the jailbreak quickly became mandatory. Their developers struggled to find breaches inside new firmwares. And eventhough they announced last year that the discovery of a low-level exploit will ensure that every firmware will be easily jailbreakable, they have yet to release an user-friendly jailbreak for 4.2.
Lately, I have decided to update my iPhone to 4.3 (beta)1. (I have been enrolled as an iOS developer for eleven months and I have not developed a single app yet. And I probably never will2.) Sure, it was not easy to give up the many tweaks that made my life easier, so to say. But in the end, it was worth it: the iPhone is much more responsive, and its battery life has never been so great.
And that would be the stallion: plain but fast.