Leave room under the workbench for your knees. You want to be able to sit on a chair while your working. A small vice or two mounted to the table somewhere comes in handy, especially for soldering. I have a power bar screwed to my bench top that I plug my tools and lights into. This way I have plenty of sockets and because of the lights I don't forget to unplug it. A power supply with different voltages is nice to have, mine isn't permanent but if I ever pick up another one it probably will be. If you don't have a ton of space a table would probably be more convenient than a bench, especially if you put wheels under it. A lazy Susan style car stand would probably be really handy. The big thing is where to store your tools - do you add room to the bench for tools or do you keep them somewhat portable in a toolbox?