depends if you are going to a high end finish elsewhere. If you have spent money on other quality fittings then don't skimp here.

My house has innocuous white sockets and switches everywhere and I was wondering if I should replace them. However when I painted the walls (Little Green slaked lime) they disappeared and they would have been more prominent if they had been metal.

We have white sockets and switches except for on one wall in the lounge. This wall has dark grey wallpaper and then sockets and gas point cover are matt silver - as colourhappy said, it helps them to disapppear. The stand out on that wall is the modern white fireplace, the white sockets were too much.

Most of my wall sockets are low down and hidden - basic cheap plastic ones. The ones on display, for example in the kitchen along the worktop are the nice flat metal Schneider ones.

I saw a nice little trick in a furniture shop who had painted the cheap plastic plug sockets the same colour as the walls, it helped them disappear into the back ground! I wouldn't do this with light switches though.