I would also like to add that since Mexico changed to CPP pays, it still lists on Movistar's website that they charge roughly 30c US per minute for incoming international calls, this is on top of the roughly 20c-30c that calling cards are charging to call cells in Mexico. So, in essence you're getting charged on both ends for the same call which is outrageous. Movistar is still by far the cheapest at $1 for 30min to the US.

I take it that at this point we can confirm that the 09 SIM does not work reliably in Mexico.

The eKit Premium SIM cards still offer free incoming calls in Mexico.

Nobody has mentioned that U.S. Cingular users can roam in Mexico for 59 cents/min. (Cost for both incoming and back to the U.S. (and I assume calls within Mexico). As DRN mentioned above, U.S. T-Mobile charges $1.49, altho my old grandfathered T-M rate the last time I was there about 15 months ago was about 79 cents when on Movistar.
Caveat: Cingular's "regular" rate is 99 cents. Before going to Mexico you need to activate the "Mexico Roaming Option" for $4.99/mo. You can cancel that add on option when you get back.

...mike