Welcome to the Mac world!
You have come to the right community to get support!
Unlike Windows, where there is so many changes between the os in every revision.... OSX stays familiar as apple releases new versions of OSX. I truly can say they improve the OS significantly.
I remember how afraid I used to be with upgrades when I was a windows only user...
Windows 98 -to-> Windows 2000 BOSD on restart... repeatedly
Windows 2000 -to->Windows XP ... Wipe and reinstall because the upgrade hosed my filesystem.
XP -to-> Vista......I don't want to talk about that one.... (I reverted back to XP...)
XP -to-> 7... painful...but at least most of my stuff worked once I reinstalled it all....... but the install still ate like 20GBs of my hard drive...
Compared to..
Apple OSX... 10.4 to 10.5...painless
10.5 to 10.6... much faster and painless install, also did I mention I actually gained hard drive space?
10.6 to 10.7... still much improved... even faster... and its the initial release.
I think its a old stigma from being a Windows User.... at least that's what I know it was for me...
Upgrade to the latest and greatest, Apple does upgrades right.