One of the Windows Vista developers unveils on his blog that Windows Vista won't support old DVD drives anymore. This means old drives manufactured before 2000, which didn't support region coding in hardware, won't work with Windows Vista.
However, this also means that people who switched firmware to make their DVD drives region free will need to use other firmware.
What does this mean for you? Almost certainly, the answer is "absolutely nothing".
First, there is no change to the way data is read from DVD drives, so data discs will still work the same way as they do today. Second, all new DVD drives will continue to run as they did before; the only change is that the risk of mis-identification as an old drive has been removed. Only if you have an old drive will you notice anything different, namely that encrypted/regionalized DVD movies will no longer play. And since the average drive lifetime is only three years, the number of such old drives that are still working is vanishingly small. Not even the optical drive test team can manage to keep their old drives alive that long.