I'm torn on this honestly. Safari (particularly mobile Safari) is literally the only thing keeping the web from becoming Chrome-only. While I would love to see Safari-alternative engines on the iPhone, I fear that the "open web" in terms of browser compatibility is cooked the day that happens: Commercial web developers are supremely lazy and their product managers are, too. They will consider the web Chrome-only from that day forward and simply refuse to lift a finger for other browsers.
I think when IE6 died, on one hand it was a relief for web developers, who (very quickly) deleted all the code needed to maintain compatibility, but on the other hand, it made the web worse by bringing us closer to browser monopoly.