Minecraft wiki entry for Nether_Portal_(block), associated text: "It is now possible to smash nether portals by simply punching them." was listed as a change that happened at some point in 1.0.0. Testing reveals it doesn't happen at all in Survival mode, so was this meant to refer to Creative and that detail was left out?
"The nether portal has been changed, having a slightly darker look." listed for Beta 1.9 Prerelease 4 in the main nether portal page. I can't seem to find any visual changes to nether portals in this version at all.. 