I only ever liked Slopes and Bedroom, all others were boring. Interiors were always glitchy with brick placement. Also, I never remember seeing a fantastic, well-liked, well-built build (not minigame) on an I&T map. All good builds had been on Slate and its various edits. Many good minigame servers were fun on I&T, I especially loved fort wars in the Bedroom.
I would not want I&T added back in, but think about what would happen if S&S and I&T coexisted together at the same time. S&S wouldn't even work with interiors because the ceiling in maps like the Bedroom would eliminate S&S's effects, rendering S&S useless for interiors. The entirety of the Bedroom would be in darkness, except where light comes in from the window.