Real nice!!
I like the streamlined foolproof GUI.
Great initial version.
 
2 things I've noticed:

- Options page is blank for me, not sure why... (I only see the "Options" heading and that's it)

- Initial seed stretching is much slower than in Python... I was hoping that Chrome's awesome JS engine would be faster at this, but well.  Or perhaps you're generating more than 5 addresses?