I'm going to say it, even if others aren't. (Atrios, for example, at least whilst commenting on the laughable antics of NRO and other Bush surrogates.)
Osama Bin Laden is stumping for George W. Bush.
He knows his appearance could be (and likely would be) spun as a boost to Bush, he's clearly quite aware that the election is coming shortly, and knows that by attacking Bush he's helping Bush make his case. In fact, by aligning his critiques with those of Michael Moore and Kerry (the "Pet Goat" bit, for example), he's subtly ensuring that they'll be seen as discredited.
(Note that I say "seen" for a reason- the point Moore made is in no way modified by its adoption by Bin Laden months later. )
He also knows that the Bush surrogates would try to catch Kerry in a bind, arguing that critics should "get behind the president" in the face of the attack. They would try (and are trying) to resurrect the "politics stopping at the water's edge" idea that they themselves discredited in 2002. The Democrats could never do this to the Republicans, as they'd screech "wag the dog" and keep right on attacking... but the Democrats' astonishing growth of spirit and backbone has only gone so far. The fearfulness and tentativeness of 2002 still lurks in the background.
(Additional Note: None of this should be construed to mean that the tape actually should help Bush, just that it can be used as a tool to do so. The media wants Bush to win, both because a Kerry win would undermine the polling and narratives that they've built up and because there's a lot of personal animosity between the media and the "patrician" (and vaguely wonkish) Kerry. Thus, if something can be spun in favor of Bush, it will be.)
Osama Bin Laden wants George W. Bush to win. The reasons are endless and obvious, even if the Republicans want to pull the wool for just a few more days. Bin Laden is closer to his goals than ever, and knows it. He wants Bush to win, and saw that it wasn't happening. Rove didn't have an October surprise, so Osama provided it.
The old saw of 2001 has returned. If George W. Bush is elected president next Tuesday, the Bin Laden has won.