Please help clear something up for this not-so-tech savvy iphone user...
I understand that with an "unlocked" phone you can choose other service providers besides AT&T, though there are some providers that are incompatible even with an unlocked iphone(?).
I am under the impression that a "jailbroken" phone allows you to load some apps that a non-jailbroken iphone can't. Is that all jailbreaking does? With something like 300,000 authorized apps available for the iphone, are there really enough great unauthorized apps to make jailbreaking worth it?
Also, I'm under the impression that when you upgrade the OS your phone is no longer jailbroken. What do you lose in such a case? Will upgrading the OS "re-lock" and unlocked phone?
Another phone that looks impressive is the Samsung Captivate (or Galaxy S). Those enhanced apps, or widgets, look pretty cool. Big display too. The DroidX looks pretty nice also. What do these phones use in place of itunes?
There are different cell phone technologies in the US, the two biggest ones (as far as I know) are CDMA and GSM. CDMA is Verizon, Sprint; GSM is ATT/TMobile, Cricket (from what I've heard) actually supports both. If I missed any providers you're curious about, let me know.
An iPhone is a GSM (only) phone. As far as I know there are no phones that do both CDMA and GSM at the same time. There are android phones on both technologies. Thus (as of right now), iPhones will not run on verizon/Sprint. There are rumors of a Verizon iPhone, but nothing solid yet.
Jailbroken iPhones allow for apps that haven't been approved by ATT, yes, this is true, but it's better than you think. In Apple's closed ecosystem, they have a few blanket statements in their terms of service/app store that will ban certain apps. For instance, until recently, Google Voice apps were banned from the (official) app store. This is largely due to the fact that google voice replicates the texting functionality of a phone, and with mobile data, no text plan was needed (shafting ATT of money, obviously). This has changed recently, when they relaxed their policies a little bit, but there are other things that apple hasn't yet "gotten up to date on" (for instance, the full bluetooth stack, you have limited functionality with the apple provided bluetooth API).
Jail breaking also allows you to install unofficial themes, functionalities, utilities, etc. One example is "tethering." You're required (except on the 2G, after some "hacking") to have a data plan with your iPhone (on ATT). You can sign up for a plan with no data plan, but they will FORCE you on one if they ever find your device on a network audit (they do this several times a month. If you get lucky, you can get away without a data plan for a while, but they'll eventually cach you). Tethering is essentially using your phone as a mobile modem. You can hook your phone up to a laptop (via a USB data cable, or via bluetooth) and use the internet via your phone. This is very, very useful for business users, or people who want to have internet on the go, and don't want to deal with the limitations of a mobile device.
So yes, your summary of "all" a jailbreak does is half true, but there's a lot more to it. You can even install VNC clients (control your phone from your computer), software to turn your phone into a wifi hotspot (alternate form of tethering), and you can also download all the authorized apps for "free" (this is STRICTLY pirating, though, but I DO NOT condone this -- I'm just pointing it out for completeness). I'm not going to discuss that any further, as it is outside of the scope of this explanation, and any further details would be a violation of the board rules.
Yes, if you upgrade your OS (aka firmware), your phone will no longer be jailbroken. Jailbreaking is taking advantage of software exploits to allow access to the file system on your phone (in more or less words). These exploits are patched (obviously) by apple every software update, so when you upgrade, the dev team needs to find a new exploit in which to gain access to your phone. You may or may not lose an unlock, but you pretty much will certainly lose it. Jailbroken/custom firmwares will often leave the "baseband" (aka the radio firmware [radio here refers to the phone part of your phone]) untouched. Besides losing your jailbreak and unlock, every time you upgrade your phone (with a clean install, at least), you will lose your apps/saved data. It's kind of a pain in the butt, but there are ways around this (aka restoring from backup, but I pretty much never do this due to garbage settings/etc going from phone to phone...).
