Their documentation doesn't seem very good... I hate actually engaging in financial matters (as opposed to discussing it), so I'm wondering how easy it actually is to claim the $50.

For example, could I just take my existing debit card and add some money to a new account in ING, and then immediately use the ING account for purchases at Amazon or for a Paypal donation, satisfying the 3 small purchases rule that way?

If it's that easy, then I think I could give this a shot. But if the easiest way involves schlepping down to my credit union to wrangle about a bank draft or mailing off personal checks and photocopies of ID or whatnot, then the mental effort is just too much, even for $50. I'm willing to do effort to get $50 when the activity is fun, like trading on Intrade, but not if all it is is financial bureaucracy.