Awesome work (as usual) scribu, thank you very much :)
I installed Proper Network Activation and it works, but I came across a couple of possible bugs:
1. upon activation, the notification on the plugin screen says it had been activated for 0/3 of my sites -- I'm guessing this is meant to be an AJAX thing that increments as it activates for each site? The first time I tried I was too quick to activate another plugin and hadn't let it activate for the third site (the p2p table for that site was missng), but then I tried again and it activated correctly (the p2p table was present for that site), but yeah the message still said "0/3" sites. A minor aesthetic issue really :)
2. I attempted to create another site, but got the following PHP error:
[17-Feb-2011 02:15:43] PHP Fatal error: Cannot redeclare p2p_get_meta() (previously declared in /var/www/venuepress.com/html/wp-content/plugins/posts-to-posts/storage.php:159) in /var/www/venuepress.com/html/wp-content/plugins/posts-to-posts/storage.php on line 161
When I went back to my site listing page, the site had indeed been created even though there had been the above error, but of course the p2p functionality didn't work because the p2p table for that new site wasn't created.
I'll have a look at the code/line mentioned above to see if I can't offer some help -- I really like your plugins!