The NIST, in collaboration with the DVD Association and the Optical Storage Technology Association (OSTA), has just finished preliminary tests on compatibility between recordable DVDs and DVD drives. The results indicated an 85% success rate. Fourteen different types of DVD-ROM drives and 50 different DVD discs were tested, and problems ranged from discs that wouldn't work at all, to freeze-ups, to video and audio dropouts. Soon, more media and more drives will be tested, including recordable DVD drives. Drive and disc manufacturers will use the results of this testing in order to increase the compatibility of their hardware.
I know this sounds a little scary, but the technology has improved and will continue to improve. Right now, it's still possible to create a disc that will play perfectly on one machine, but not at all on another, but this is becoming less common. While not scientific, my experience with compatibility generally has been quite good.