Well, for one there are a fair number of equations, which ebook readers are going to struggle with. Plus there are "structural puns" which depend on lines aligning and breaking in a certain fashion.

Here's an example page from Amazon's preview:

http://img26.imageshack.us/img26/8082/screenshot20120118at14...

Note the musical extract, the heavy use of blockquotes, etc. It's pretty much a worse case for an ereader.

PS: I'll admit I'm a bit late to this party, as I just bought my copy for the Reddit readthrough, and it's the first actual dead-tree book I've bought since my Kindle. I too was annoyed at first by the lack of a ereader version, but after reading the first few pages of the intro I couldn't imagine reading it any other way. This is a VERY dense book where I often find myself flipping back a page or two to reference earlier material.

So, none of the examples given so far convince me.

I remember a couple of bits where you get multiple levels of nested indentation, to the point where the text started half-way across the page, and those would be difficult on most e-reader screens.

You would lose something when converting to ebook, no doubt. But the convenience might also make it worthwhile.

(Stretched analogy: I have heard that Pink Floyd's vinyl album Atom Heart Mother was cut so that at the end, it just kept playing the inner ring in a loop instead of finishing, so you got the repeating sound of a dripping tap. That would be lost as an mp3, but I'd still rather have the digital version.)

The popular e-reader formats are all HTML subsets. I really don't think the formats actually could render the equations faithfully, without just making images out of them, which means they are either going to be paginated awkwardly and generally be hard to read.

If you had a large format reader that could do PDF properly, that could handle it though.

Hofstadter cares a lot about form, and thinks it is intimately connected to function. I believe in the end of "I Am a Strange Loop" he said that he edits every single line of text so it fits evenly and aesthetically across the line. In other words, each line must stretch to the far right of the page, but the letters can't be stretched out/separated too much. This must be extremely tedious to accomplish.