Personally, I prefer the HTML emails and find them faster to go through. It takes me about 2 seconds to skim a Thinkgeek mailer with product images and see if there's anything interesting, vs. having to actually read the entire email and click a bunch of links.
Then there are all the nice graphs and colors in the server monitoring emails I get that let me get a big picture overview of the server farm health at a glance every week. If I see any red or too many spikes, I can decide whether to investigate further or get back to coding.
For all the benefits I get from HTML email, I'll risk the small chance that getting an email with Paula's pink hearts theme will seriously fuck up my day.