I just ran the upgrade tool from my admin cp..  All was going smoothly until reaching step 2, and then this:

Declaration of IPS\Content\_Item::hide() should be compatible with IPS\rules_hook_ipsContent::hide(IPS\Member $member = NULL, $reason = NULL)

Now my site is down with this:

[[Template core/front/global/globalTemplate is throwing an error. This theme may be out of date. Run the support tool in the AdminCP to restore the default theme.]]

and I can't access my ADMIN CP at all!!

Please help.  I've submitted a support ticket but I can't have my site down like this. 

This has been resolved by REMOVING the "Rules" 3rd party app.  Really wish this automatic installer would check what applications you have BEFORE beginning the install.  Maybe it does and I don't realize it but then it missed this completely.

Be nice if it deactivated all 3rd party apps and plugins before updating, then reactivate them on completion and sandboxing them like WordPress does on plugin activation.. any PHP error and it will auto deactivate that plugin.

Sort of related, the Member Map Beta application is not compatible with 4.1.6 either.  I had to disable the application after the upgrade due to the inability to view profiles.

Patches available here for this error:

http://ipsguru.net/forums/topic/145-rules-breaks-416