Bonded alu/carbon frames were top of the line in the early '00s before full carbon. I owned a few, including a Kinesis, a KHS Flite 2000 and 720(?) and some other boutique stuff. They all rode great, and I never had any reliability issues. If they can figure out bonding carbon and alu in a demanding application such as aerospace, then they can do it for a bike frame.

Only downside: slightly heavier construction than full carbon. Nevertheless, these frames & bikes now sell for next to nothing, and if kitted out with say, Dura-Ace 7700 or 7800 or Campy Chorus or Record will perform as well or better than any current 'performance' road bike regardless of how much you pay. Performance being measured as speed over long distances and the ability to hang with the fast crowd.