I use my BofA card strictly for purchases in country. Most banks now...no matter if they are BofA, Citi, or many others are making foreign transactions subject to the 3% fee, regardless if the transaction is made is USD or a foreign currency. Apparently, the merchant, by virtue of being "foreign" makes them higher risk. It is all hooey. I've always thought the foreign transaction charges were bovine fecal matter, but USD charges from foreign merchants is just plain greed. Check to make sure whoever does starwood's card doesn't do the same thing.
I've a separate VISA card from my Credit Union which only charges 1% on foreign transaction fees...and to top it off, when I use my ATM overseas, they don't charge me $5 for the privilege of accessing my own cash.
I'll stay with the BofA card, simply because the companion ticket is worth the $75 annual fee, considering where I have used it.