In terms of changes, the visual tweaks settings section in the options known as "Bells and Whistles" has been "exposed." You could reveal the hidden section (really, an Easter Egg) by perseverance, but now it's there for all to see. You can change visual styles, and if you want, on an iPhone 3GS, turn on a setting that shows a moving waveform when you search by voice. As Google suggests, don't try this with a slower iPhone.
Also, search results open directly in the Google Mobile App now, not in Safari. You can switch to safari if you want, but as Google says, "This will get you to what you need faster, which is always our goal at Google." They're not necessarily picking at Safari, though they could if they want.
Additionally, Voice Search adds accents and languages. Not only are Mandarin and Japanese supported, but if you talk like an Aussie, for example, Voice Search can handle it.
Of course, the Google app that many would love to see on the iPhone is still MIA. That is, of course, Google Voice. Who knows if it will ever show up, and although it's possible to use it within the browser or on a jailbroken iPhone, it would be great to see an official app.