I finally got around to attempting mavericks on it but unfortunately I couldn't get around the still waiting for root device error. It's something with just my computer but if you need any help then let me know
If you formatted the hard drive to GUID, then you don't need and don't want to use the mbr patch. After you install mountain lion, install the patched IOATAFamily into S/L/E with Kext Wizard and repair permissions and kernel cache with it.
Also, the DSDT edit in post #1 may help with the still waiting for root device issue too.
Adding a timeout of 7 or so to chimera may not be a bad idea either since it's giving the components time to boot up.
In my experience, Using the -f boot flag would help eliminate that error too if all else fails since it takes longer to boot due to ignoring the cache
If you're using the onboard graphics, I'm surprised it's working at all. Unfortunately, I don't think so as most of the older legacy Kexts are x32 and made back in snow leopard days. If you look around you might find something though. I'd recommend just buying a decent graphics card. With the 6670, I had dual monitors out of the dvi and hdmi ports. The VGA port didn't work.
Tried the upgrade to mavericks, went well the 1st time no issues and all systems were working as they should
Because I use the dell as a Plex Server, unfortunatley there are still a few bugs in the Plex application with Mavericks that need to be fixed. Been on the Plex forums and is a very common issue for those who have upgraded.
So, back to Mountian Lion 10.8.5 until this is sorted. Good to know that the upgrade went well without a hitch though.