11.5(1)SU1 essentially forces you to stop using Internet Explorer Compatibility View. Read the release notes and make sure you aren't forcing intranet sites to be view in compatibility mode via Microsoft GPO before the upgrade.
Seeing a FATAL message when rebooting may be recoverable. A bug CSCvb21486 Reboot of node may result in FATAL error was hit after deploying UCCX 11.5(1) with ES01 but Cisco has it associated with CUCM. It appears to be related to the automatic VMware tools installation gone wrong. You'll need to grab a recovery disk and bravery as my damaged file seemed to be on the wrong partition. It looks like this:
If you are using Prime Collaboration Deployment to execute upgrades, note bug CSCuu34496 L2 upgrade status shows as running instead of complete from OS adminpage. Your standard L2 upgrade may finish without issue but never report so. You can see in the install_log upgrade_install.sh|release_upgrade_lock: Releasing lock (pid: 15496)|
Calling Search Space for Redirect on your triggers by default is set to Default. This means that UCCX will route calls through the application and script called by the trigger with the caller's CSS, not the trigger's CSS. If your caller is not capable of reaching the agents or other destinations defined in the application and script directly your call will be rejected. This is typically not an issue but where you might have PLARs set up with very restricted CSSs, sending the PLAR to a UCCX trigger may fail. This can be modified per trigger on at least UCCX 8.5 and beyond. See bug CSCso91760 at https://bst.cloudapps.cisco.com/bugsearch/bug/ 20CSCso91760 for more redirect information. See http://webmaxtor.blogspot.com/2011/05/cucm-ring-down-phone.html regarding basic SCCP PLAR setup.
The official Cisco install guide indicates the server hostname is case sensitive and must be lower case. I suspect this is to alleviate issues with installing signed certificates later with all lower case SANs.
When modifying "Finesse Layout XML" it appears restarting TomCat or Finesse services is no longer required. Users seem to have to log out and back in to see changes though.
If you are deploying UCCX 11.0 you should plan to hit bug CSCux33949. Your default Finesse gadgets will all be broken. At this time the fix requires TAC gaining root access, providing some new JAR files and restarting the UCCX Engine. Budget time to have this fixed early in your implementation plan.
RTMT cannot be used to show telephony data on versions 11 or 11.5 per bug CSCuy72411. We won't be able to use it to check triggers, call control groups and CTI ports until who knows when.
UCCX Editor is not compatible with Windows 8 or 8.1.
The Team Performance gadget served by /desktop/gadgets/TeamPerformance.jsp is not resizable in version 11.0. The rumor is it will be in 11.5.
As of version 10.0, UCCX Finesse supervisor and agent desktop still shows all queues and all logged in agents. See http://www.cisco.com/c/en/us/support/docs/customer-collaboration/unified-contact-center-express/118823-technote-uccx-00.html for guidelines regarding modifications.