Honda iDCD (Dual Clutch Disk) hybrid system they say is not reliable in long-term use and many owners have complained of iDCD failure and errors in long-term use. In newer hybrid technologies such as the Honda Sport Hybrid i-DCD system (in the Vezel and Fit GP5) the chances of defects are higher.
Vezel uses Li-ion batteries that have a large initial energy density and efficient charging compared to NiMh batteries but customer experience with current Li-ion phone batteries suggests they will be dead within four years no matter how well one cares for them.
Fuel efficiency is determined by a lot of factors. Most Toyota Hybrid Synergy Drive (HSD) vehicles are very fuel-efficient. The Honda IMA is not very fuel efficient; in fact it has been called a "mild hybrid."