I bought and fitted a new SSD earlier in the week to try Win 8 out properly, assuming it would be happy dual booting with Win 7. All went pear shaped.
I installed Win 8 on the SSD fine, it finished and booted up and the first thing I noticed was there was no boot menu, just straight into Windows 8. Looking at startup options, (once I managed get out of metro to find where they'd ruddy hidden it) Win 7 was not listed as a startup OS and the Win 7 HDD was not even visible as a drive in explorer.
Restarted into BIOS and the Win 7 drive has also disappeared from the boot order list when in numpty mode but luckily I could select Advanced mode and boot from it. Win 7 could see Win 8's disk fine but not the other way round and for some bizarre reason, my Win 7 installation that has been running fine for years now suddenly needed its network adapter removing and reinstalling after each boot and shortcuts such as manage computer were broken.
So be careful if you are planning to dual boot, took me ages to sort the mess out. Win 8 itself was rubbish BTW.
UPDATE, after doing more googling I'm pretty sure this was because I was using Windows 7 in RAID to use another SSD cache drive enabled via Intel Smart Response. Guess this rendered the drive invisible to Win 8? The other weird errors though, I cant explain (cache corruption, dunno? Unlikely). Think I'll stick with the copy of Win 8 I've got running in Parallels on my Macbook for the time being.