The lesson for Snapchat, and really any new software company, is that design updates need to roll out slowly. You cannot drop a boat load of changes on users. Facebook learned this early on when they introduced the new wall and news feed. Now they allow you to preview design changes before they get fully rolled out.
The design changes aren't necessarily bad, it still looks and operates fine. Snapchat just made the rookie mistake of changing everything at once before anyone could orient themselves around the changes.
Facebook, LinkedIn and Twitter all did this. They're all spammy and terribly broken crapholes which I now barely use. If there were viable alternatives I'd eliminate that barely.
The design changes aren't necessarily bad, it still looks and operates fine. Snapchat just made the rookie mistake of changing everything at once before anyone could orient themselves around the changes.