Try (in another AT&T store, preferably) to buy one for their no contract plan. That would probably be the cheapest way. Is the phone worth it? That's for you to decide. It's a nice phone. (I wouldn't take an iPhone for free - I got royally screwed by Jobs once, and that's as many chances as they get at me.)
As far as throttling, you get unlimited WEB BROWSING, not unlimited data (that's what the TOS says). If you use too much data (and what "too much" means depends on where you are, how much usage the tower gets, who is making the decision, what phase the moon is in, and what some alien in another galaxy had for breakfast) you get throttled.