JMich: In which case you may be interested to know that IE9 and IE10 are notsecurity holes. XP may be a bigger security hole than the current versions of IE, and since XP can only go up to IE8, that does mean security holes galore.
And IE10 when run as a 64-bit application is even more secure as well.
Darvond: But still less secure than competing browsers due to a lack of helpful utilities like noscript and adblock plus.
Enhanced Mode (aka 64-bit) only allows controls that are 64-bit (and I think signed as well). Add to it the fact that it doesn't require Adobe Flash (it has its own flash implementation), and you've also removed quite a few threats. True, scripts may still be executed, but not everything, and I'm not sure if it will allow access to the system.
And I'm 90% sure that the metro version doesn't allow any access to the filesystem, other maybe from the open and save dialogs, but for that you will have to ask Elenarie.