Bought a iPhone 4 and was happy to find out that it can be used as a wi-fi router. And just think, and whether has sense to pay for two mobile Internet on iPad and iPhone, if you can pay for the Internet only on the iPhone and iPad to connect via wi-fi. In the end, the iPhone is always with you, and no iPad. Among the shortcomings can only see different times of operation of these devices, and if the iPhone sat iPad was left without Internet. But in such extreme cases it is possible and SIM card change.
Is anyone using this scheme? There are other drawbacks (maybe the speed drops or something else)