If you aren't eligible for upgrade but upgrade via 3rd party..

[blueprint1983]

I have a 3GS that is not eligible for upgrade through AT&T. However, I can trade-up via Radioshack's iPhone 4 promo for $25+tax.

I already know this:

1 - I will lose Applecare since it will not transfer to the iPhone 4 (since it's an upgrade).

I don't know this:

1 - Will I have to get another 2 year commitment with AT&T?
2 - Will I have to pay AT&T extra for upgrading my iPhone since I am ineligible to upgrade? (doesn't seem fair since I'm not buying through them?)

I would assume yes but expect the worst because AT&T would know.

 

[rrandyy]

Are you sure you can upgrade through radioshack? All radioshack is doing is reselling AT&Ts service. My bet would be either you are eligible for both, or for neither.

 

[Goldinboy17]

I have a 3GS that is not eligible for upgrade through AT&T. However, I can trade-up via Radioshack's iPhone 4 promo for $25+tax.

I already know this:

1 - I will lose Applecare since it will not transfer to the iPhone 4 (since it's an upgrade).

I don't know this:

1 - Will I have to get another 2 year commitment with AT&T?
2 - Will I have to pay AT&T extra for upgrading my iPhone since I am ineligible to upgrade? (doesn't seem fair since I'm not buying through them?)

I would assume yes but expect the worst because AT&T would know.

1 - Of course you'll need to renew your 2 year commitment to AT&T, they're giving you a heavily subsidized phone.

2- Early upgrade fees are $399 for the iPhone 4 16GB and $499 for the 32GB. Radio Shack is only reselling their service for a commission, you're still getting the phone from AT&T. If you actually qualify for an upgrade through Radio Shack than you also do from AT&T. They check the AT&T server when you ask to upgrade.

 

[Applejuiced]

I have a 3GS that is not eligible for upgrade through AT&T. However, I can trade-up via Radioshack's iPhone 4 promo for $25+tax.

I already know this:

1 - I will lose Applecare since it will not transfer to the iPhone 4 (since it's an upgrade).

I don't know this:

1 - Will I have to get another 2 year commitment with AT&T?
2 - Will I have to pay AT&T extra for upgrading my iPhone since I am ineligible to upgrade? (doesn't seem fair since I'm not buying through them?)

I would assume yes but expect the worst because AT&T would know.

Radioshack, bestbuy or wherever you go will tell you the same thing.
You are not eligable for an upgrade so AT&T will not pay to subsidize your phone purchase. You'd either have to pay full price ($599 or $699) or do an early upgrade if your AT&T account qualifies for $399 or $499 for the 32GB and if you do you will sign up another 2 year contract. No way around it.
First you need to learn how carrier subsidies and cellphone contracts work in general. What you think is fair or not or who you're buying from doesnt make a difference. Radioshack is not giving away iphone's for $25, there's many other strings attached in order to get that price.

 

[mpossoff]

I have a 3GS that is not eligible for upgrade through AT&T. However, I can trade-up via Radioshack's iPhone 4 promo for $25+tax.

I already know this:

1 - I will lose Applecare since it will not transfer to the iPhone 4 (since it's an upgrade).

I don't know this:

1 - Will I have to get another 2 year commitment with AT&T?
2 - Will I have to pay AT&T extra for upgrading my iPhone since I am ineligible to upgrade? (doesn't seem fair since I'm not buying through them?)

I would assume yes but expect the worst because AT&T would know.

Sell your 3GS for around 200-250 and use the funds towards partial upgrade of 399. This is what I do every year.