I do think the GTX 580M provides the best overall user experience with support for Optimus switchable graphics as well the potential future-looking graphics performance seen in our Ultra quality settings test of Battlefield 3. The NVIDIA Verde driver program is also a benefit over what AMD has traditionally done in the mobile market. The NVIDIA driver team has been releasing mobile-compatible driver updates on a much more regular basis than AMD has been and in most cases are running version-for-version with the desktop parts."
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips