Who you calling a layperson? I sir am a priest
Let's just say that I have been writing about ebooks and working in ebooks for a long time.
I realize we're just jabbering in all good fun, but I usually experience several moments of disgust every time I try to downconvert an epub file to a kindle.
Again, I ask you, how many people are using Netscape 4 these days?
It's true that people still buy their kindles and that Amazon carries 50% of the ebook market, but the kindle format hasn't been updated. And if you remember, the people who complained the most about Netscape 4 or IE 5-6 were the web designers --- they spent wicked amounts of time dumbing down their web designs so that things looked noncrappy on multiple platforms.
It's true you can switch out css on kindle ebooks, but Kindle also requires different semantics as well...
The biggest problem with Kindle is they're stuck with having to maintain a legacy format -- it's unlikely that many ebooks published over the last 3 years will ever be upconverted by publishers....
I'll just mention one thing: images. Images had to be jerryrigged to work in the Kindle e-ink devices. When people start using Kindle tablets to read their old purchases, those old purchases are going to look terrible....