Yep, it's a pretty aggressive firewall, so it's definitely a good idea to check the comments first, and then work through the site after enabling of course (I had issue with the thumbnail on my blog page which were being blocked by thumb|timthumb| in the request strings, and have had to comment out RewriteCond %{QUERY_STRING} ([a-zA-Z0-9]{32}) [NC,OR] to access and download my backups). I think this is why it's still in beta, as it really needs to be tailored to each setup, rather than the 5G which worked out of the box.
Cheers!