For the most part the svn nightly seems to work just fine. There are a couple, very weird and very specific issues. If you do either of these actions, your cache will get wiped out:
1) Edit your BP profile
2) Send a PM
Other than that, I haven't found any issues! You can change your notification settings and you can post to the 'wire' without a problem, but those two things kill the whole cache every time.
So far, I have the following set to never cache:
wp-.*\.php index\.php activity register members groups