I don't know a single start up that actually builds their own html emails.<p>It is a part of the industry that has been entirely replaced by services, similar to web hosting.
This is going to be a welcome change. Especially since this will work exactly like the old IE fallbacks. I'll be keeping an eye on which organizations use these in their emails and which don't. :)
I know I speak for everyone in saying how delighted we are that the spam email we never signed up for and can't unsubscribe from (and never open) will be better looking on our phones.<p>Thanks Google!