In the release notes gcc 4.5.3 is mentioned as experimental. Can someone explain how "experimental" it is? Is it in some ways less reliable than 4.3.5? Or hasn't it been tested as thoroughly as 4.3.5?
The 4.5.3 release has had limited testing so you are more likely to encounter unknown bugs than with 4.3.5. For work projects that don't require specific 4.5 features, I would recommend using 4.3.