I just bought my X10 yesterday even though I had read about the white disc problem. I have made a number of test shots of bright lights in dimly lit rooms but have not been able to reproduce the problem. I shall be using the X10 extensively over the weekend to see if there is really a problem in normal use.
The only "issue" I have experienced is that it does not focus accurately sometiimes. This is easily fixed by reactivating the autofocus which will then usually lock on correctly.