I've always found curved hallways to be terrible for TF2 gameplay. It encourages blind fire around corners (IE spam) and prevents tactical ambushes. It can also imbalance teams depending which direction it turns, even more so than a corner, and can contribute to stalemates due to the danger they pose whilst traversing one (like anti-cover).
But that's just me. Maybe i hate it more because everyone creams their pants when they see a curved hallway in TF2 simply because it goes against the games aesthetic/layout status quo. I'm not universally against curved walls, they look great in games where they fit, HL etc... I just don't like them in TF2.