Its the way up there with the sequential numbering. Especially I-90 being reversed (E to W) instead of the usual W to E. Then I-87, has three schemes due to three different jurisdictions as you have the NYC Deegan (though maybe NYSDOT, but influenced by the city), the Thruway, and the Northway all with their own exit numbering each. New Yorkers refer to all three named roads as a different one and not as the whole I-87.
VT is another one that loves its sequential numbering and probably don't want to give it up as they are so used to it all. NH is another, as MA is planning to convert, and CT will change the numbers when the signs need replacing. RI, I have no clue what their opinion is on it, but being its such a small state having milebased numbers won't change things much. DE started with kilometer based on DE 1, but still both I-95 and I-495 have not been changed, and the Turnpike in NJ you can ask JeffandNicole the answer to that one.