While I don’t have a need for another charger, I have been curious about seeing how well they actually work given their supposed standardisation when used with compliant devices such as the Nokia Lumia 920.
They are a bit pricey compared to regular chargers and simple USB cables so whether or not you can justify the convenience of charging your phone without plugging it in will be up to you. I have played with wireless chargers before in the form of the Powermat with the add-on cases for devices like the iPhone which unfortunately blocked some of its ports but for the cost I couldn’t make the jump to purchasing the solution for myself.
I guess the good thing about Qi is the standard and future devices will be able to re-use what you’ve invested in now but it could well be cheaper as more people adopt these wireless chargers. The question will be whether or not you are willing to pay more to be an early adopter.