Just tried installing Exchange 2013 CU5  and is pretty much easier  and went clean without any errors/warnings in my lab setup.

For the changes and fix that have been done in CU5 can be referred in my previous article

http://exchangequery.com/2014/05/28/microsoft-exchange-2013-cu5-released/

The setup can be downloaded from this location

http://www.microsoft.com/en-us/download/details.aspx?id=43103

As we are aware that the upgrade order from Exchange 2013  if we are using separate server for mailbox and cas then Microsoft recommends to upgrade the mailbox server first and then the cas server.

After the download is complete just open the setup file and it opens the below screen.Choose the required option its always recommended to check for updates and then click on next.

 

 

 

The setup starts copying files .

 

 

 

And then initializes the setup as below.

 

 

 

 

 

Finally it brings the upgrade option and just click on upgrade

 

 

 

Click on accept in the license agreement and proceed with the installation.

 

 

 

Now the setup goes through the prerequisites analysis

 

 

The setup starts once the prerequisites is completed.It goes through 18 steps as below for organization preparation.

 

 

And then the installation continues  in 9 steps and completes the installation as below.

 

 

 

Just reboot the servers after the installation is complete.

We can now notice the new service Microsoft Exchange Shared cache service is installed on the server.

 

 

For unattended installation/upgrade you can refer the below technet article.

http://technet.microsoft.com/en-us/library/aa997281(v=exchg.150).aspx

Cheers

Sathish Veerapandian

Technology Evangelist