Hm, looks like I misremembered and there were only 6 types. The exact types are proprietary info but the original author gives a few examples here: https://www.quora.com/Gmail/What-are-the-six-types-of-email-...

I've just done a bit of googling around to try and find more on this. I've turned up a heap of references to the developers finding 6 different types of users during their 2 years of internal testing before launch. Alas no where is there actually a list of these 6 different types of users.

The doc in question was written by Kevin Fox who replied to this quora thread about it, but dodged the question claiming that the info isn't his to divulge.

http://www.quora.com/Gmail/What-are-the-six-types-of-email-u...

Weird.

I'm pretty sure I'm not on that list. I've never liked the way the gmail web client works.

* I've always disliked conversation view, and I keep ending up turning it off whenever I try it

* The lack of ability to sort emails is really annoying

* The layout of emails, particularly when trying to reply to an email, I find confusing - in particular it would make far more sense to have the text box at the top of the page

That being said, I probably dislike it less now than when I first started using it so I think the changes have generally been positive.

On a side note, I think Photoshop is also a UI disaster area.