We need this topic to cover every different part of the world (maybe a nice sticky wiki article to keep updated?).
We are in Europe and choose hippocket WiFi. Is a French company that now use the free roaming option in the EU to let omyou use mobile data pretty much everywhere in Europe.
After almost 2 months, has been ‘ok’ we had some issue and sometime the speed was shit due to some technical issue (they give you some fallback extra sim tho, so we just needed to wait for them to activate a new sim, although if we would have an urgent need we would have been offline no chance).
My best bet in Europe is to do A LOT of research on top up plans (or contracts if you stay long) across all countries and actually go to the country with the best deal (so far I think 3Drei in Austria) get yourself a SIM card, buy yourself a WiFi dongle (mifi) and get going. Also a local backup sim could help. Really depends how much you need internet. We work online so we couldn’t play around too much.
Another problem is: watch your data! When your phone is connected to the WiFi dongle it thinks your home and start backing up all your stuff and burning a lot of data, disable all automatic use of internet or you going to have to top up very often!