Remember that you can convert the voltage, but wattage and frequency are also important. Anything with a heating element is going to require upwards of 1000w, which requires a big heavy expensive converter. Also, anything with a motor in it is going to run nearly 20% slower on 50hz (UK) power instead of 60hz American power. That's why things like blenders and electric shavers don't work as well.
Generally, the only things that work well on either system are solid-state electronics like laptops, mobiles, and digital cameras. And those just happen to be the kind of stuff that is dual-voltage out of the box, imagine that.
My rule of thumb is that if it requires a voltage converter, it stays on one side of the pond.