Three things I care about in an email service are: deliverability, deliverability, and deliverability.

Oh, and also open rate and response rate.

I use a few different email programs but what they all have in common is that they don't show images by default and even when I tell them I want them show images for emails from a particular source, they never seem to remember to do that.

I like the idea of fancy looking emails in principle but if it gets in the way of people reading them they can go to hell.