I assure you that your T-Mobile plan will not be available for use with a T-Mobile iPhone.

Whatever it ends up being, I'm sure it'll be a better deal than ATT/V.

Pricing game theory suggests that T-Mobile should undercut AT&T by a small margin at most.

It depends on what you mean by "not available for use." Any standard T-mobile plan that includes data (even the $5 T-Zones plan) will work with the iPhone. The only problem is that it's Edge-only.

True, you can possibly rig it up with an unlocked AT&T or other non-T-Mobile contract bound phone.

What I do with my iPhone 3G. But as parent said data is only on EDGE.

People have been running iPhones on T-Mobile since 2007. The reason this is so big is because the iPhone currently doesn't support CDMA.

Correct me if I'm wrong, but if you jailbreak your iPhone and use it on T-Mobile's network you will only be able to use the EDGE/2G network as the iPhone's 3G radio uses different frequencies than T-Mobile's 3G network.

Makes the choice seem a little backwards then doesn't it?

Exactly. That's why I'd rather use Android over iPhone.

I'm hoping for one that uses their HSPA+ technology that gives 42 mbp/s of blazing speed.

You're correct, except that it is "unlocking" that allows you to use an AT&T iPhone on another carrier. "Jailbreaking" is completely different - it simply allows you to install unsigned software.

One must jailbreak their iPhone before it can be unlocked, because you need to run special, unsigned software to unlock it.