Caution: different devices have different USB amperage requirements for running, charging, etc.
Example: if your USB adapter is putting out 1A and you try to run an iPad from it with screen on, Wifi/ 3G etc., the outlet probably can't keep up. I don't know if the iPad would detect this and shut down or if you'd blow a fuse in the adaptor or what. In any case, charging a sleeping device is easier than powering an operating device.
Check the input demand of your devices, and the output of your adaptor.
I just bought one myself (haven't used it yet) that has two ports: one is 1A, the other is 2.1A. Being different outputs, it probably makes sense to be mindful of what I plug into what.