At my workplace, we've upgraded straight from Windows XP to 8 a few months ago. To date, the Start screen has just mainly served one very useful purpose - Going into Desktop mode.
I certainly much prefer Windows 8 over XP at work. Despite running on just 3GB of RAM and 5-year old hardware (Core2Duo 3GHz), it flies in comparison to XP. The Windows XP installation took at least 5 minutes to fully boot, most of the time at "Applying computer settings" when logging in. Windows 8 is straight to the login screen in a few seconds and loads the roaming profile in 20 to 30 seconds. Windows 8 also performs a heck of a lot better with multitasking than XP and far better network performance. XP was a pain for intermittently dropping network drive connections. The last clean Windows XP installation only temporarily improved things.
As for Windows 7 vs. 8, it's hard to say which I prefer, i.e. I like Windows 8 for its better desktop mode features such as the improved task manager, copying files info box, etc., while I like Windows 7 for its native Start menu. I have Windows 7 & 8 on my home PC as dual-boot, but so far I haven't seen any reason to start using Windows 8 over 7. Sure, Windows 8 starts up a heck of a lot faster, but I only boot my PC once a day apart from the odd occasion I need to reboot. Unlike the drastic difference I've experienced between Windows XP and 8 at work, Windows 7 seems to perform just as well as Windows 8 on my home PC and all my software runs just fine in Windows 7. However, if there comes a time when I need to use an application that only works or works better in Windows 8, at least I've it ready for use.
So what's my main advice about Windows 8:
Pin all regularly used software to the taskbar and always use the right mouse button at the bottom-left for everything else. That's exactly how I use Windows 8 differently to Windows 7.
By pinning software to the taskbar, you can open recently accessed documents by "dragging" the software icon up from the taskbar, much like how clicking the '>' next to software on the Windows 7 Start menu (including third party replacements) brought up recently accessed documents. The Windows 8 Start screen doesn't seem to have the capability.
By right-clicking the bottom left, it is possible to go directly into the command prompt, control panel, file explorer, etc.
Finally, I use the Windows Key + R to quickly launch accessories, such as calc, notepad, etc.