Compilers and tools for Linux ... have been regularly tracking the latest development
1.5.7 and 1.5.8 upgrade the compiler and other tools, using the (non-IDE) "Toolchain" from Atmel. This is close to the latest available version of the compiler (for better or worse.) It contains some annoying incompatibilities with older arduino code.
Actually, they stopped doing that a while ago (1.0.3?), because it was a complete disaster. Many of the linux "packages" of avr-gcc were defined incorrectly and didn't work, and many other installed versions of the compiler that were not compatible with Arduino. Recent versions of the IDE for linux include their own static version of the compiler tools.
So far I've only seen issues related to the AVR PROGMEM hack.