HSPA USB sticks is how a lot of people connect to the net in Europe. In fact I'm looking at setting myself up with such a device when I go on vacation for the month of May in Portugal. What I'd actually prefer is a battery-powered HSPA-to-WiFi bridge like the MiFi. But I'm looking to rent/borrow the device rather than buy.

That DataJack seems pretty low speed. The European providers are advertising rates like 20Mbit now. Should be fine for email though.

Similar to the way the SIdekick plan will not work on non-sidekick devices, the SIM for these product may not allow you to connect to the network unless it's stuffed inside the appropriate dongle...