[Sirtel]

For myself, I always delete half-title, praise, other books by author or publisher, next reads and other ads. I usually leave the inline TOC, just in case (unless it doesn't work - I've seen it just copied from a paper edition with nonexistent page numbers and no working links), full title page (I like to look at it when I open a book for the first time), copyright page, indexes, introduction and dedication.

As to homogenizing my reading experience in regard to fonts, margins, line-height et al, yes, absolutely. I need it to be the same in all my ebooks. Anything else distracts and annoys me.