I think it all depends on what type of email you're getting. I send Hacker Newsletter (http://hackernewsletter.com) out every week, and I based on past feedback and some testing, a rather large percentage of my 12k+ subscribers like the HTML version. Why? Well, I include a LOT of links in each issue (one to the article and one to the HN comment for each of the ~35 stories I include), and HTML is way easier to scan in this case.
If however you're getting an transaction type email just to update you on something, then yeah, text might be better.
Comments
I think it all depends on what type of email you're getting. I send Hacker Newsletter (http://hackernewsletter.com) out every week, and I based on past feedback and some testing, a rather large percentage of my 12k+ subscribers like the HTML version. Why? Well, I include a LOT of links in each issue (one to the article and one to the HN comment for each of the ~35 stories I include), and HTML is way easier to scan in this case.
If however you're getting an transaction type email just to update you on something, then yeah, text might be better.