We lost an Abrams in the Euphrates in OIF. No way the driver was getting out and all 4 were actually KIA. The escape hatch on the bottom of the M60 is sometimes mentioned as desirable, though not when you here stories of them being lost along the way (especially during amphibious ops).
Depending on the fuel discipline needed, NBC can be used as AC on the M1A1. It's mostly not needed, though. You're sweating like crazy anyway, what's a few degrees. I know in Iraq, highest I recall my ammo temp was 127 and that's 10 degrees cooler than ambient...