Last summer I wrote about Curve coming to the U.S.. It’s a single card that you use for purchases that lets you assign the charges to your choice of rewards cards from your wallet, and even re-assign those charges later.

I received my Curve invite on Wednesday, and several readers have told me they received theirs as well after signing up for the waitlist back in August.

Benefits,

• Earn rewards in addition to what your credit card gives you. For the first 6 months you earn 1% back on purchases using Curve, on top of the miles or cash back you earn from your rewards card that sees the charge (so if you have a 2% cash back card you’re actually getting 3%). Note that the top 100 people on their waitlist get 10% back (capped at $1000, then 1%) for their first six months.

  You can get an additional month of that 1% back for each friend you refer as well (refer up to 3 friends at a time, then start over).

• Go back in time to change which card you’ve charged to which is great if you make a mistake and don’t use the card with the best category bonus, or you are approved for a new credit card right after a big purchase and would rather assign the charge to meet the new card’s spend target. You have 30 days to ‘change your mind’ about which card you’re using for a given charge.

  Their ‘Go Back In Time’ feature could save a lot of relationships between the rewards-obsessed and their spouses. Let them your spouse put charges on whatever card they want, no more arguments, and just move the charges onto the “right” card later. Or maybe you didn’t realize a purchase was going to get coded as travel, and so you realize you’ll earn more points by moving it to the most lucrative card for the travel category.

Drawbacks,

• Only Mastercard and Discover work with Curve along with Diners Club. You can’t use it with Visa or American Express. That’s severely limiting.

• I worry about issuer risk Last fall the UK issuer of IHG and Marriott cobrands cancelled the cards of cardmembers who used those products with Curve.

The card isn’t broadly available yet, but you can sign up for the waitlist. But they’re inviting some of those who were already on the list to apply, so Curve is now real in the U.S. I plan to apply to play around with it.