So far I’ve only had the opportunity to test how WordPress 2.0.1 handles sending of automatic trackbacks (in the Options|Discussion tab, we’re presented with a checkbox that
says, “Attempt to notify any Weblogs linked to from the article (slows
down posting.)”

What that means is that for any article linked to in a particular
post, wordpress should automatically be sending a ping to alert that
article that you’ve written about them, saving you the time of having
to manually paste their trackback URI into the Trackbacks section of
the Write Post screen.

On what was initially my WP 2.0 Test blog (and which is now my WP 2.0.1 Test Blog), I had reported that in WordPress 2.0, the only blogs that seemed to receive these automatic trackback pings were other WordPress 2.0 blogs.

I had hoped that these problems would be resolved in
WordPress 2.0.1, but instead they seem to have worsened, with even more
erratic results than before:

• again, no trackback pings to WordPress 1.5.x blogs or TypePad blogs got sent
• again, the only time WP properly sent a single ping to a referenced post was when it was pinging the same version of wordpress, this time from v2.0.1 to v2.0.1
• duplicate pings were sent to WordPress 2.0 blogs that were referenced in a wordpress 2.0.1 post, AND
• duplicate pings were also sent to wordpress.com blogs that were referenced in a wordpress 2.0.1 post - making you look like a spammer

What a bummer.