Not to really throw a wrench in the works but here goes...
Mozilla anything is free. It is a continuous public work in progress. Therefore, if you are going to use it... then you should want and try to make it better by working with it instead of finding a bug and running to some other one. What are you going to do when you find a bug in opera? Run? No, you will have to pay for it... or you will get banner ads and load up your system with a bunch of spyware and stuff. This will eventually slow down your pc and you will be in the same boat again. Only difference is that wmv files will run natively instead of being ported.... which i think is really a stupid reason to leave a program that is as great as anything mozilla. 
Just like linux, freebsd, unix... etc they are all free and a work in progress and depend on us (geex) to help them find and fix bugs and problems with the product we are building together. Remember, without programs like this... we will begin to pay more than a fortune for programs... 
So, to finish my rant/realization... dont quit using it because of a small bug. Report it, and try to work it out with everyone. I use 3 different browsers myself. IE,Firefox, and Mozilla. I like the ability to have multiple browsers because i like to contribute. Just like i run Ubuntu at home for an os and xp pro as my main os. I like to tinker. 
Dont run... be a man.... stand up for something besides your money and the amount of food you get on your plate compared to the dude beside you.... thats what life is all about.