* > 100 minutes -- correct. If you have no funds in your account, you will not be able to make calls after 100 minutes.
* Tethering -- Correct. At that point, you're starting to have to compare what you use in talk. $30 + $15 tethering = $45. If you spend another 50 minutes talking, you're at $50, which is the price of the Unlimited talk/text/data (1gb at high speeds) plan. 150 extra minutes gets you at the 3GB price point, 250 minutes gets you to the 5GB price point, where it would be cheaper to be on that plan.
* Int'l Data - Correct. None.
* Port -- Yes. You need to do it upon activation, or within two weeks, I believe, otherwise it will cost you. If you do not know T-Mobile service in areas you intend to use it, I do not suggest porting until you've tried it.
* You need to order the SIM from http://prepaid.t-mobile.com or you can buy the $30 plan activation kit from Walmart (we generally suggest buying from Walmart if possible -- there's no questions about it that way). You NEED to activate the $30 plan as you start as you cannot change to it later
* After 5GB you get slowed to 2G speeds. Some people say it's prohibitively slow, it's not horrible, just not exactly useful for media. This is the same after you hit whatever GB in the other plans.
* No international options with prepaid plans. You need a Simple Choice plan for international options.
* You can use a credit or debit card with this plan. Prepaid folks have two options for payments -- credit / debit card attached to their account or go out and buy prepaid refill cards. The refill cards allow a combination of anonymity with their account ("Honey, I just went to CVS to pick up a few things, that's the charge on the credit card" vs "Hrmmm... how can I explain this T-Mobile charge to my wife without her knowing I have a secret agent phone?" [see what I did there? I didn't go naughty!]) and also allow people full control of when refills happen and ensure they're paying the proper amount when they expect. Some people have also found ways of getting these cards at a discount (e.g. if you have a credit card that pays out rewards in Staples gift cards and you go to Staples and buy refill cards with your rewards).
Great! Thank you for the response!