I've been using aluminum kettles and HLTs for over a decade and never had them impart off flavors. Palmer also notes that aluminum will not, on its own, corrode or impart metallic flavors under the pH and temperature conditions encountered in brewing; it is quite nonreactive under a pH of 9.0, and he explains why even galvanic corrosion in conjunction with other metals is not normally an issue in homebrewing. But don't clean it shiny, let it acquire a dull gray oxide layer. Then it is totally passive.
(My most recently acquired aluminum pot came with manufacturer's instructions not to treat or season it in any way, as it had been specially treated to passivate it at the factory.)