The "old" email notification subject header was clear, concise, identified the cache, and told me the nature of what happened to the cache.
Ex. [GEO]Notify: Reviewer#1 published BigCache (Traditional Cache)
For me, the "new format" is far less user-friendly and makes me have to guess what the notification is about.
Ex. Instant Notification: BigCache (GCXXXXX) has a new log from Reviewer#1
The "old" format told me all I needed to know. The "new" format tells me nothing of value and requires me to open the email before I can glean what the notification is about. I use the subject headers to decide which notifications to open first. At least, that's what I did with the "old" format. The new format is a step backwards from efficiency.
I vote for the "old" format, as the "new" format is most unpleasant.
Plain-text in the email was just fine, too. From my perspective, the graphics add nothing. I am fully aware that it is Geocaching.com that sends the notifications and I don't need graphical banners in the body of the email (that take up space that I have to scroll through) to repeatedly remind me who sent it.
Just my opinion.