I have serious concerns about their whole business model, particularly their lack of privacy protection and the fact that they (not you) apparently own the data that is generated.
When signing up (or at any other time) you can select to not have your results used in research. As the article linked above notes, you need to opt in to have your results available for research.
Yes, you are the product (if you're okay with that), but you can opt out and still get your full results. I agree that them never deleting their records of your genetic data is a bit dodgy, but they're not allowed to use that data if you don't let them.
And to some extent, I can see why we're not allowed to dictate what someone else erases from their computer. Looking at non-health comparisons - would it be reasonable to demand that our banks or creditors erase all data they have compiled about us? Certainly not, but the comparison is a bit weak, since health data is seen as being far more personal, and something which we played a big part in "producing".
The article has a very good point when it says "It’s hard to say exactly how those rights will play out, however, since none of this has ever gone before a judge." It's really undiscovered territory, with no clear parallels to be drawn from other areas. If 23andMe were doing the ethical thing, they'd delete their copies of patient data upon request - it would look better, and probably very very few people would request it, especially if the process were a pain in the butt.
But they are a business, and will ultimately do the most profitable thing, rather than the most moral thing. And failing to delete results is probably not eating into their profits to any significant amount. Hence if change is going to come, it will almost certainly be from the results of lawsuits and/or legislation. It's a bit distasteful, but it's exactly what every other major corporation does.
For myself, I found it to be highly worthwhile. If using my genetic data and questionnaires as a product to sell to companies means that we can continue to get great results for very cheap, I'm pretty happy to support that. I also think it's sufficient that people can opt out of having their data used if they want to, even if that option isn't ideal.