Copper will leach chemicals at high temperatures. Just like an aluminum pot, you'll want to boil the copper manifold for about 10-15 minutes to build a passive oxygen layer, and you'll be OK. Also, you don't want to clean the manifold with oxyclean or scrub it at all, as this will destroy the passive oxygen layer.
Other than that, it poses no real problems.
Primary #1 - Midnight Ryeder (Midnight Wheat and Rye)
Primary #2 - Florida Weiss
Primary #3 - Kane-DOH APA (Honey Citra APA)
Secondary #1 - Downtown Flanders Brown (brewed August 2012)
Keg #1 - Raspberry Florida Weiss
Keg #2 - Cinnamon Raisin Cider
Keg #3 - NONE!
Bottled - NONE!