Mostly with you .... Only thing is that developers do not really need to use Safari to develop code. All they are writting is Ajax and they can use just about any browser that is JavaScript and AJAX compatible. While Safari compatability is probably the best, it is not the only choice. Peple been developing AJAX apps for several months before Apple decided to release Safari for windows.
I am not aware of anything in Safari that will significantly make development any better / faster. It is just a browser.
Yeah, neither am I. It could just be to ensure total Safari compatibility. If there is anything, I guess we'll be hearing about it in the next few weeks.