Thanks very much for the response. Your first comments were posted after I read mia's post but before I had completed drafting my follow-up, so I never saw it until now.

I am starting to understand. Bottom line, pay in full.

I understood the consequences to be bad, but receiving a $50 finance charge for the one month I left $1200 on the card was worse than I ever could have imagined. Thankfully Citi gave me a "grace period" of my own, and returned the $50 in full.

This makes the Citi AA debit card I used for 2+ years seem like a good alternative by comparison.

Thanks for the explanation.

I do have one question though:

Citi is running a promotion for 20k miles + the potential for 10k more the first year and 10k more the 2nd year. Others have stated that they have 2 or more Citi cards. To make sure I understand this thread... If I had 2 Citi credit cards (or any 2 credit cards with this type of billing/calculation of finance charges) and paid all debt in full each month, could I alternate charging to the 2nd card when I could not pay my first card in full so as to minimize the finance charge?

EXAMPLE - let's say I spend $2,000 each month on my credit card and pay it in full each month. I want to spend $3,000 one month (vacation, whatever) and will offset this by spending $1,000 the following month. Is it better to spend $3,000 on the first card in the first month and then spend $1,000 in the 2nd month on the 2nd card while paying $2,000 toward the first card's balance? Then in the third month pay $1,000 on each card + the finance charge on the first card accrued in the 2nd month? No new charges on the first card during the 2nd month would mean I was only paying a finance charge on past charges and not new charges, right?

Thanks again.