A gotcha that's not listed is the limit on characters that you can store using localStorage: http://arty.name/localstorage.html
I wonder if the behaviour is different if you have multiple smaller documents?
I came across this after experiencing problems saving files to PlayBook using HTML5. The main problem seems to be size but there's also a limit on how many items you can write I think. Didn't test it too thoroughly, came up with workaround involving splitting files.