PDF has the advantage that no receiver of the file can make changes to it.
It also has the disadvantage that it's designed to display things
exactly like the original. This is not a good thing when it comes to e-book readers, since their screens are considerably different sizes than a computer screen (the Astak does a fairly good job at text reflow on pdfs, but it's just making the best of a badly suited format). PDFs are considered one of the very worst formats when it comes to e-book readers. On a computer, on the other hand . . . I
love PDFs! So it really depends on the purpose. Having a variety of formats is good for that reason.
The Kindle, probably the most popular ebook reader of all, doesn't support epub, strangely enough.
I avoided the Kindle and nook for reasons precisely like that--I wanted lots of options for file formats, not just one or two. For small files, I don't have to convert everything to a specific file format, which is really nice. For the big stuff, I can either use Calibre for a quick convert if I'm in a hurry, or paste into Sigil for the nicer look.
Looks like Sigil saves as just epub.
Sigil IS limited in its output format, but it was only designed as an epub editor, because there wasn't anything out there easy enough for newbies yet powerful & featured enough to produce quality files. Since epub is the best format for the Astak, I figure I'll just create that when I do need to convert.
