One thing I find annoying is I have to lug my Fonts from the previous OS to the new one. I have over 700 Fonts in my FontBook and they are all ORGANIZED into Collections.
I'll show you how to bring in all your fonts AND your Fonts Collections into your new system, follow along.
Obviously you keep a copy/clone of your old OS boot drive just in case something does not work in the new one and you need access to a specific app: boot from the clone and PRONTO! You're in business.
1) Start your computer from the new OS boot drive. Mount your old OS boot drive.
2) Go to your previous OS home folder / Library / Fonts. Copy all the Fonts content from that folder and Paste it into the new OS home folder / Library / Fonts.
3) Go to your previous home folder / Library / FontCollections. Copy all the FontCollections content from that folder and Paste it into the new OS home folder / Library / FontCollections.
Copy from old OS boot drive / Users / "your user" / Library / Fonts
(And then do the same with FontCollections)
Paste to new OS Home folder / Library / Fonts
(And then do the same with FontCollections)
4) Open Font Book and check that everything is in order.
5) Enjoy! You are welcome!
Note: if you do not see the Library folder, select your Home folder in the Finder Sidebar, then Select View, Show View Options, check the box "Show Library Folder".
