But what about my situation?
I have an iPhone. BUT I bought it only a few months after getting a different phone that was subsidized.
According to this, I have an iphone, so I can upgrade. Or do I need to wait until my upgrade cycle is up?
The AT&T memos I've read haven't put any conditions on qualifying for the subsidized price if you have a first-gen iPhone. So based on a strict reading, yeah, if you have a first-gen iPhone you can do something like get a free subsidized phone from them on July 1, get a subsidized 3G iPhone, then sell your free phone on eBay for some nice cash back.
I have two thoughts on this. First, it's deliberate on AT&T's part and they realize they might lose some money in such transactions but figure its worth moving more 3G iPhones. Second, their real intention was to say that owning a first-gen iPhone, even if you bought it two days ago, has no impact on upgrade eligibility since it was unsubsidized - but if you're not upgrade eligible for some other reason, like getting a free phone two days ago, you're SOL for the subsidized 3G iPhone prices.
Personally, I'd imagine that the second is more likely, but who knows. That means if somebody got a subsidized phone from AT&T two weeks before getting a first-gen iPhone on launch day, they'll be in for a shock when they can't get a 3G iPhone for $199 or $299. We'll see.