[duck]

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.