What kind of setup did you have to do for blo.gs, blogrolling, technorati, and weblogs to pickup up the pings? Or do they, like Google Reader automatically opt for push?
I also know that sending pings to multiple places slowed down my publishing (technorati alone often took tens of seconds and even would occasionally time out). Hopefully, there is enough critical mass around PuSH now, so that those that crave real-time updates will fetch the data from there.
On a somewhat related note, I just added code to ping the hub when there is a change in my overall comments feed. I have not yet decided what I want to do on my comments feed per post.
The delay problem is why WordPress switched to sending them out asynchronously one slow (or currently offline) hub could take a normally speedy publish process and dramatically slow it down.
WordPress certainly has a different scale problem than I do (that’s putting it mildly). I only get a handful of comments per day, so I opted to do my pinging on the Apache thread. That being said, I do daemonize the process first so that the response is sent to the commenter either before — or concurrent with — the sending of the ping.