A standard for trademarks is risk of confusion; as the "!" is not pronounced (or typically indexed), the collision between 'Go!' and 'Go' is much stronger than the others you list.
If the 'Go!' creators had any hope for using that name on a series of offerings (tools, books, etc.), they have to object to Google's use, to retain the presumptive rights they'd established so far via use.
If the 'Go!' creators had any hope for using that name on a series of offerings (tools, books, etc.), they have to object to Google's use, to retain the presumptive rights they'd established so far via use.