Besides the fact you pay a toll at it (when 59 is free) or it requires you to get off of Eola and take a different road to get to the entrance ramp (or the exit ramp does not drop you off on Eola). There is the little fact that nothing really tells you what the toll is for that entrance/exit. Finally there is the little fact that traffic on Eola also is horrible.
Other than that, great idea.
It's like when they got rid of the Hillside Strangler and someone I know who worked for IDOT told me "all they are going to do is move the congestion a bit further east" how right he was.