Specifically, the segment along the Mon.

• Reclamation of land for productive development.
• Elimination of a massive, miles-long barrier that makes crossing the Mon even harder than it needs to be.
• Reduction of noise pollution along the bike trail and around Mt. Washington (the sound carries across the water).
• Elimination of hilariously dangerous blind urban on-ramps that highway "engineers" squeezed in wherever it looked like it would fit on their little 1:100 scale black-and-white 2D drawings.
• Reduction in the number of unnecessary bridges to be inspected and maintained (elevated highways and ramps are bridges).

A comically expensive undertaking, to be sure. Hence its position at the bottom of the list. The more logical solution would be to have never put it there in the first place. Now it's gone all metastatic into the regional fabric.