Frankly, I had utterly ignored drag and drop tabs in Safari. This feature didn’t work in older versions of the app and only appeared in Safari 3, so I hadn’t yet adjusted to it. The recent article on tag dragging modes at Daring Fireball comes about a week after my own interest in the feature suddenly piqued.
So, yes, drag and drop for tabs appeared relatively late in Safari’s development. I fail to use this feature even though I’ve wanted it for a long time. Together, these facts buttress my conviction that certain features need to be in a product on day one, or they will not get used. I refer to this as the “PageMaker window” problem, for it wasn’t until PageMaker 6-ish that you could open up more than one document at a time in PageMaker. By that time, I’d been using PageMaker for long enough that I had user interface scar tissue built up around the single-window limitation. Even though I had a feature I wanted, it was left unused most of the time.
Even if I did want to use tag drag and drop, its behavior in Safari is weird. I probably wouldn’t have taken the time to understand what was going on if it hadn’t been for the DF post. Or, at least, I wouldn’t have realized there were different modes at all. (It’s like user-interface-by-Zork-text-adventure. You have to discover the odd set of steps — which make some sense in hindsight — that drops the critical key from the keyhole onto the placement you’ve carefully slid under the door.)
My own experience with Safari 3 has shown that if the tab is the leftmost one in a Safari window, dragging it in any direction results in both the inter- and intra-window drag behavior described on DF. That’s the only tab position that works in this manner, though.
I also thought that holding down Option or Command during a drag would make a difference; I could swear that happened last week when I tried drag and drop, but I must be wrong. I can’t reproduce it today.
Update: There’s an older article at Betalogue that describes tab drag and drop, and mentions the behavior of the first tab.