It will work in the US and some other non-Digicel countries, but at rather high rates(best used sparingly or if nothing else works when roaming off Digicel).

Best used on Digicel Caribbean networks because of the DigiRoam preferred rates. A note that Digicel also has coverage in some Pacific island countries; might also have good rates there.

Not sure. But, as you mentioned, I know the digicel sims have very good roaming rates on other digicel networks throughout the Caribbean.

My wife used the SIM for four days in (the former British) Guyana and it worked great and pretty reasonable.

The Bahamas and Mexico are two places I still need to work on.

Which sim? The dual or the UM +44?