A recent leak claims that Ubuntu's new Snap Format is not secure - http://news.softpedia.com/news/developer-claims-that-canonical-s-new-snap-format-isn-t-secure-on-ubuntu-desktop-503287.shtml. Since reading the article, I have been having second thoughts about upgrading. Are there any workarounds available to upgrade.
As I understand it, it only means that as long as you use X11 Snap doesn't provide any additional security over using e.g. apt packages. So you will need to remain just as careful about your software sources as before.
When running on Mir, supposedly Snap provides much better isolation between applications (sandboxing), which could provide more security when using software from less trusted sources.