It still has ~$20USD (~60 minutes) balance which expires in June 2012. You can buy additional airtime online, or via the phone, or at any T-Mobile store in the US.

SIM has 718 New York area code phone number right now but you can change that to whatever you want.

You'll need an unlocked GSM or T-Mobile GSM phone to use this SIM.

This is a great way to save money while you're down in the States, as opposed to incurring roaming charges on your existing Canadian cell or your phone not working at all in the States (as is the case with SO). This is a great solution for emergency situations and you can use it to call anywhere in the US or anyone in the US can call you at your local rate.

Included with the T-Mobile prepaid plan –
No annual contract. No credit check.
National coverage with no roaming charges
24/7 customer care
Voicemail, caller ID, and call waiting

Also, with T-Mobile prepaid service, you can qualify for Gold Rewards after you put $100 of credit on the account. This means that every top-up after that gives you bonus minutes, plus a 365 day expiry. Simply put, you can keep this SIM going for as little as $10 a year after you qualify for Gold. I've put $40 onto this SIM/account so you're almost halfway to Gold Rewards already.

Thanks.