Most of the plug in hanging lamp units I have come across I find they are great for supplemental lighting. I personally do not find that they are terrific for overhead lighting but that is my opinion. Most of the lamps out there are stylish, cute and can be used for craft tables, sewing rooms, and accent lighting.
Naturally, with many of these lamps you can change out the shades or the bulbs. This is not always the case, but if you are looking for a plug in that is going to work for your dining room, for instance, you might want to look carefully for one that you can adjust the bulbs on so that you can get the right amount of lighting needed at all times.
I think they can be used just about anywhere, but I have noticed that some of them are better for accent or supplemental lighting rather than lighting you will need in a kitchen or at a desk. Still, they can be draped and arranged pretty easily as you can plug them in and move the cord however it works best for your particular needs.