Like Raytech mentioned lots of bugs to resolve just like any new technology, hands up anyone who is brave enough to be the first to buy Microsoft's latest OS.
With any new technology I would always be cautious and critical of claims espousing the benefits. Having worked in R&D in the automotive sector for many years I tested many new technologies, many of which never made it to market. The added complexity and management systems required for the cells will create extra maintenance costs regardless of how reliable they are or claim to be. This aside one thing is for sure they will gain market share in the next generation, costs will come down and this cycle will continue.