I have same board as you and also just updated to W8 Pro, installed on SSD but only have HD4000 at the moment. I'm using the latest beta bios A71 and thought I'd take a look into this as part of getting my install nicely configured.
The MSI Fast Boot also has a utility app to switch this on and off within Windows from the system tray, i.e. load stay resident app. This app doesn't appear to be available from MSI UK website, I had to download it from the US site, on motherboard product page.
With MSI Fast Boot switched on with the app (also enabled in BIOS), I'm assuming this is with the switch covering the word 'Off' and the word 'On' showing, this toggles the MSI Fast Boot option in the BIOS to enabled when the word 'On' is showing in the app. The app is also useful as a neater way of getting back into the BIOS rather than repeatedly hitting the Delete key during boot up.
I think you also need hibernation enabled as some people with an SSD may be used to disabling it, if it's not enabled you won't have the 'Turn on fast start-up' option in the 'Power Options' > 'Choose what the power buttons do' > 'Shutdown settings' section.
This is not as fast as some of the W8 demos I've seen either so I thought I'd enable the W8 Feature in the BIOS which has caused me some grief as it then failed to boot and dropped me into the EFI Shell as shown below. What's more I couldn't get back to the Click BIOS for a while as resetting the CMOS resulted in the reset BIOS screen where you need to press F1 or F2 but it had lost my wireless USB keyboard / mouse connection. Eventually after moving the Logitech Unifying receiver to another USB port and resetting the BIOS again it regained connection with the keyboard/mouse so I could choose F1/F2 but still ended up in EFI shell where I had to enter 'exit' to escape into Click BIOS.
Whether I have MSI Fast Boot enabled or not seems to make no difference, either way I achieve around 20 seconds from a cold boot.
Even though I'm using an Ivy processor with Z77 chipset I can't get the Windows 8 Feature in the BIOS to give me W8 Fast Boot. Unsure whether this is due to not having a discreet graphics card or a fault with the BIOS? It seems odd that if the BIOS doesn't detect suitable hardware that it wouldn't make the feature unavailable.