I purchased one of those three Mi-Fi devices. The HUAWEI E586 that you can run up to 5 Wi-Fi devices at once.
After about 5 minutes i get the dreaded yellow triangle on my desktop limited connectivity. The signal is 100% on the router and on computer.
Looking at all the forums this is an issue with the network adapter and windows 8.1 whenever windows updates. If i put the sim from the Mi-Fi device into a normal dongle i have no problems
Even though these forums are littered with the problem, very little info on rectifying the problem as this has nothing to do with three, but windows 8.1 and Microsoft updates to the network adapter