only the sim from the three nokia smartphones e71,6790,or the e5 will work.
or you can now buy the sim to put in your phone. the rest of the phones that straight talk sells, the sim is locked to the phone.
I received my AT&T Samsung Galaxy S 2 (non Skyrocket) yesterday, popped in the SIM card from my Nokia E71, deleted the existing APN's with the APN Backup & Restore app, then added the Straight Talk APN from the Straight Talk BYOD website and everything works great.
Should be the same on the Skyrocket as the non Skyrocket.