The Diamond doesn't have an Extended ROM area. I found out that Opera doesn't get installed if you reset it before it customizes, but that's not a problem. Just look in the \Windows directory for WM6_PPC_HTC_Opera9_WWE.CAB file. I installed Opera to the storage card and saved nearly 10MB of space!
Sprint TV and a few others won't get installed either. There are a few text files to look for in the Windows directory if you want to see what doesn't get installed. Look for: Config.txt, Config_AP.txt, Config_operator.txt and Config_PT.txt. They list what is installed during the customization along with the path of the file if you want to manually install it.
I can't say wether or not it affects my phone. Looks like I won't get activated until Tuesday! GPS works, so does WIFI. Even after installing all the same stuff I had earlier, I now have 35MB of free space available. I installed anything that didn't run on the today screen on the storage area, including Opera.