There have been problems with the latest intel chips on Linux, and even on well supported chips I've had trouble with weird resolutions, multi-monitor, etc. I'm currently using an AMD 785G chipset based motherboard which comes with a Radeon 4200 - the open source drivers for this actually work, including enough 3D support for desktop compositing. It's more stable than the proprietary driver for my old GeForce 8800. (no crashes or corruption so far)
That said, Radeon 5xxx series support is in its infancy.
For best results on Linux, usually the latest anything is best avoided, while issues are worked out. It depends though, and things are improving a lot.
True, although intel have been very good about this in the past, and to some extent still are - there are often drivers in the kernel and in X.org for IGPs which haven't even been released yet.
I've also run into regressions on older hardware that no one cares to trouble-shoot because not enough people are on the setup (e.g. the soundcard on a PowerBook 667MHz for example).
That said, Radeon 5xxx series support is in its infancy.