Based on my experience for the two minutes for which my device was jailbroken, I saw little difference between a jailbroken device and nonjailbroken device. All I noticed was a little Cydia icon. Presumably I can add software via Cydia, but I'm curious to know what else jail breaking offers out of the box on an iPhone 4 running iOS 5. Is Cydia really the only starting point, or do other settings magically appear in the Settings app or elsewhere? Are there other benefits?
My understanding is only Cydia. Everything that changes the phone via jailbreak comes in via Cydia. :)
That'd be correct. Cydia is your gateway to everything that makes the jailbreak remotely worth it. At current, there are several jailbreaks that greatly enhance Siri's functionality, among a host of other goodies.