The IE losses and Firefox gains are an old story. Microsoft was holding it's own against Firefox.
The more important story here is potentially that Google's Chrome is gaining share much faster than Apple's Safari. This highlights the power of Google's open source software model, as compared to Apple's integrated hardware-software strategy. This is the software versus hardware / software model, of course, is what doomed Apple in its first battle to the near-death (against Microsoft). It is worth watching this one closely.
The trend gets more interesting as Smartphones and tablets replace laptops and desktops. The browsers installed on these smartphones are Safari for iPhone, iPad, and iPod and Chrome for Android devices. Market share will be greatly affected as smartphones increasingly gain momentum.
Below are stats on the numbers from Net Applications. Check out that steady Chrome growth. Notice the small Safari gains have been despite the proliferation of Apple devices. These are signs that Google has got it right.
Image: Net Applications www.netmarketshare.com