Yeah, now everything is wildly more powerful. Basically, the entire game would devolve into rocket tag much earlier. Magic classes and monsters would both become much more powerful, while non-charging mundane types would all fall short. Even one-hit-killers like those would find themselves too vulnerable to reliably use that tactic without initiative boosters.
In addition, initiative would also spike dramatically amongst PCs. If everything can take you to critical hp in one round, everyone wants to go first. You only need 1 hp to deliver a kill-strike.