Seconded.
I was seeing *serious* slowdowns yesterday in my Gmail account, in desktop mail apps (taking 30 seconds or longer just to log in), this is on a 90 Mbit wired connection.
And then OAUTH (authentication) was broken for a few hours.
Finally, today, my Gmail account on the iPhone (stock Email app) has wrong message states (read/unread) and unread counts, no matter how many times I refresh.