I just bought a DVD+RW, Why did I choose DVD+RW? Because even Walmart and the Grocery Supermarkets here are carrying DVD+RWs. My supermarket only sells CD-R, CD-RWs, and DVD+RWs for example.
When a media starts getting sold at those places you KNOW the market is either already saturated with those drives or there is a strong belief it will be.
Just for the record, I wouldn't I buy media at those places but it just gives you an idea of which standards have the most backing.
Good prices on media can be found here:
MeritLine