Earlier today I had to give up on reading the 7-8-9 or so pages of Entering the High Holy Days that I had planned for today. After about two hours I still hadn't managed to get more than half-ways, and it was going slower and slower and slower. And that's after giving up on notes and correcting erroneous highlights even earlier. Two hours for a few pages of reading, some highlights, one note, and a couple of quick reference checks!
First things first: this happened with a just restarted computer, no other programs open, no swap file, and -- when I first looked in the Activity Monitor -- well over 500MB of free RAM. So that's not the problem.

Also, before starting this reading I did three short readings in other tabs (without either highlights or notes, if I remember correctly), so the normal background work after startup ought to have been already finished by the time I got to this resource.
Yet this tiny bit of highlighting took me something between five and ten minutes, with long beach balls between each:
(I think the screenshot above was taken during one of these.)
The one very simple one sentence note that I managed to make before giving up took me 10-15 minutes. The problem was no longer just that Logos couldn't keep up with my (slow) typing. This time it wouldn't even cache the keystrokes and write them all to the screen later. The first attempt resulted in "On RH the leader is changed here instead of later and these become the first words of the main service." showing up as this (minus the last 3-4-5 letters):

A second attempt at typing in the whole end only added those last few letters above. After that it went down quickly. I had to add letter by letter, with beach balls between first every three, then every two, then every single letter. Adding the missing words in the middle was even worse, because it lost focus every time. Letter one. Beach ball. Click to position the cursor. Beach ball. Letter two. Beach ball. Click. Beach ball. You get the picture...
Click on another tab. Beach ball.
Click on another place in the TOC. Beach ball.
And so on and so on.
Log: 7120.Logos4_120911;17.52.log.zip (Should it really be syncing that much?)
(And, yes, the font size in the note is way larger than my setting tells it to be: http://community.logos.com/forums/p/53903/395515.aspx#395515.)