According to various "industry and channel sources", one analyst is reporting that the 5th generation iPods are selling better than expected... even exceeding iPod nano sales in certain markets.
Businessweek points to 5-7 day delays in fulfilling orders of the 5th Generation iPod from Apple, however, this may simply be due to constraint in certain supplies. Apple is reportedly shopping around for a second supplier of LCDs to relieve the constraint.
Apple has already announced that they have sold over 1 million videos, but its hard to correlate that to 5G iPods sales, since anyone can purchase a video to play back on their Mac or PC.