I'm not sure what you mean by builds, but I'll assume you mean animiations.
I have tested with 8 animations on a slide (all set to on-click, as that is what is required to be able to cue your animations in Presenter), and they are work and can all be syncd with the Sync tool or by adjusting the click markers in the audio editor.
Presenter only counts the on-click animations and will show "X animations remaining"
I do mean animations, and I'm not sure why it's working for you, perhaps if you added some more...? I have 10 and I've tried it with multiple slides. I also have timings that were already done and working in Presenter 7 that aren't working at all when I export with 8. I've tried with other presentations too, same results.
Another unrelated issue that I found in the meantime is that some graphics that look okay in PowerPoint have a big black box after exporting instead of the transparent background that they're supposed to have.
Yet another issue is that I have my settings set so that the presentation does not move on to the next slide until the user clicks "Next", but the presentation rolls right from the end of the audio on one slide and moves to the next without clicking anything.
This program scares me, I'm sticking with 7 until there's an update!