When did Apple launch a phone without a physical button on it, for the home screen? I also don't see three virtual buttons for home, back and task list on my iPhone...

Or do you mean that the new iPhone 4S is made of cheap plastic? The one we have at work looks like glass and aluminium. But the materials look and feel so alike, I suppose it is an easy mistake to make.
I could understand the original Galaxy S, it did resemble the iPhone 3GS, but the Galaxy Nexus doesn't look anything like an iPhone (3GS or 4). And the physical screen size on the Galaxy Nexus is huge!
It is the same with the Galaxy, slim and plasticy with big shiny "SAMSUNG" letters at the top of the screen, stands out against an iPhone!
My girlfriend's Megane estate looks almost identical to the Corolla estate of the same year. Likewise, a new Opel Astra estate drove past us on Saturday and I had to do a double take, I thought it was an odd looking Golf Estate at first glance.
The case, here in Germany, was that the Galaxy Tab looked "just like" an iPad, even though it was a different form factor, had "SAMSUNG" in big silver letters on the case, was made out of cheap plastic and, when turned on, had weather widgets and a clock on the home screen, which the iPad can't do... The whole case was around look-and-feel (no patents, as software patents aren't recognised here), and having played with both, I can say, that there is no chance of mistaking them. The iPad feels much "squarer" in the hand and the Tab, which feels cheap and plastic in the hand, it is much smoother to use than the iPad.
Samsung seem to be going very much their own way, making cheap-plasticy feeling devices...
As to "slide to unlock", all Android devices have had that since 2007, so it seems a bit bogus to go after one specific manufacturer - apart from it being the latest, official Google Phone, as opposed to a re-branded and re-skinned version of Android (i.e. the phone has the vanlilla Android experience, not Samsung's TouchWiz).
That said, when the patent was announced back at the end of the summer, looking at the wording, the official Android, htc's Sense and Samsung's TouchWiz, or even Windows Phone 7, were infringing on the wording of the patent.