i know of a few people in my city who have had composite decks done by deckbuilders and have had issues with the decking,, the manufacturers replaced the material but the homeowners had to pay to get hte decking replaced if it was over 2 years old,
the most recent person had trex decking put in and it was stained upon arrival,, it was still installed by the deck builder however since it was so recent every thing was covered
i should mention ive done quite a few composite decks myself, the first being timbertech which i found to be complete junk.. it shatters when cutting it, it requires a color match trim on the ends as its a hollow core decking,, even worse a year later it had faded so bad you'd think it was 10 years old.
the product ive had the best success with and will continue to use is the azek decking