In IE11 windows 8 call to window.localStorage was throwing out an access denied error. Using try and catch manages the issue and allows the script to execute in IE 11 in desktop mode.
I think it is a problem with IE11 rather than the way Silverstripe is implementing the preview via an iframe from what I have been reading. http://blogs.msdn.com/b/ieinternals/archive/2009/09/16/bugs-in-ie8-support-for-html5-postmessage-sessionstorage-and-localstorage.aspx. It seems that the way IE11 deals with localStorage is broken in certain cases but I am not 100% certain of the cause yet as I have not been able to find a definitive answer. I only noticed it was a problem when a new client said they couldn't view the admin screen properly in IE11. I took a look in IE11 and I was experiencing the same problem which makes the admin interface layout screw up and the preview doesn't work due the error mentioned in the first post.
Instead of the original code I submitted I have amended it and added an additional function to test more robustly to see if localStorage is available and can be accessed properly. It is a copy of the code on a blog post Mathias Bynens has written about detecting if localStorage is available and can be used: https://mathiasbynens.be/notes/localstorage-pattern
I have added a console.warn as you suggested if localStorage is not available so that at least you get a warning if localStorage tests fail.
I have tested this on Windows 8.1: Firefox, Chrome & Mac: Firefox, Safari, Chrome and it seems to work as expected. On IE11 it displays the admin area correctly now but obviously doesn't save the preview settings between page loads if localStorage is not available.
Once you get a few sites under your belt most devs would likely turn to using environment files to names DB credentials. This introduces this a bit earlier to get them used to the simple idea of an environment file.
Eventually I'd like to rewrite the installer to generate this over storing in the _config.php.
BUG Fix TreeMultiSelectField using the wrong label
BUG Fix encoding of selected title on TreeDropdownField
BUG Fix DataDifferencer trying to compare non-comparable fields (non-dbfield objects)
BUG: Fix issue with TreeMultiSelectField not saving
BUG: Fix issue with GridFieldPrintButton
ENHANCEMENT Instead of using multiple api calls to encode dbfield values, delegate this operation to the individual fields via forTemplate
Instead of using a new API to communicate html encoding to treeselect, just ensure all content is HTML encoded, and enable html_titles in jstree.
NEW TreeDropdownField sanatiser helper added
Use config for default_cast of objects
FIX Determine if Diffed value should be escaped
Forcing casting for core DB fields
Fixing permissions labels
