Most of the complexity is in the electronics. But electronics love complexity and its reliability is not compromised by mere circuit design complexity. Auto makers have had decades to evolve under-the-hood electronics reliability to the parts per billion level for mass production of tens of millions of vehicles/yr. There is new technology/risk with the power device heat exchanger technology. But, GM will do intensive environmental, vibration, reliability, QA, FMEA, PFMEA, testing and evaluation. The short Volt development schedule may cut into Pilot evaluation. The EV underhood environment is far more benign than in an ICE.
Maintenance: No tuneups, EGR, hoses, mechanical linkages, engine lubricating oil, spark plugs, transmission oil fluid, vacuum leakage issues, degradation of high voltage ignition insulation (rubber), or heat degradation. Less break wear.
Overall, I think the tradeoff is on the plus side. Undoubtedly there will be great improvements and learning form Model 1.01 to 2, but this is just the inevitable march of progress.