One month ago upgraded my server. Everything went fine BUT..
New upgraded mod_security rules + firewall totally screw up the upgrade enjoyment.
Row mod-security installation is just way overkill for dynamic sites.
As a result i am still having unhappy visitors who was blocked from the server just for publishing 4+ links on one of the vbulliten based board.
I would suggest that you LW guys re-tune your mod_security rules according to the real needs of your clients.