My biggest annoyance in the new one apart from the horrible colors was how the buttons change position or disappear depending on the context. Much less intuitive than the old design.
Its a shame that Google decided to force the new design, I would just leave the old one as optional as it was during the past few months.
Actually my point was exactly that everyone seems to have their own favorite thing they miss about the old design. So for me it would make more sense to build a mode (on top of the new codebase) that would mimic the old design instead of implementing fixes one-by-one. Then everyone who liked the old design better could just change one setting that is easy to find and be done instead of playing with bunch of individual settings in different menus to achieve the same thing. I think it would stop a lot of complaints even if it would not be perfect.
I understand that there might be very good reasons why it is not feasible, this is just my 2 cents.