I am an old pro with desktop publishing and have been using Indesign for many years, and Quark before that, and PageMaker before that.
Some things I need in APub:
Ability to import native Indesign and PDFs and edit them as native APub elements, not as graphics.
Ability to preview color separations and overprints.
Ability to flow text to multiple text boxes, break text flow, reverse text flow, insert text boxes, delete text boxes and maintain flow, etc.
Full paragraph and character style support with nested styles and auto apply styles
Robust table support with cell styles, copy and paste rows and columns, repeating headers.
Full PSD and AI support, along with AD & AP support
Find and replace fonts throughout document
Find and replace text by story, document
Basic effects such as dropshadow, feather, fade, blend
Full corner options
Object styles with size and attribute controls
Script support such as importing multipage pdfs on each page and calendar creation
Ability to embed, unembed, relink, break link, etc for all kinds of links
Robust text alignment such as lock to baseline, multiple baseline grid, vertical justify within box.
Preview with bleed, without bleed, with and without guides
Robust spell and grammar check
Support for different binding beyond saddle-stitch, including perfect bind and coil bind
Warning if multiple page sizes exist in a document
Industry standard pdf output with full transparency support, RIP tested pdfs
Full spot color support from day one
Logical master page behavior, link pages to master, break link to master, convert objects from master to page level objects
Presets for pdf export, text import, document setup, print
Easy and logical header and footer, page number and section support
Well, that is what comes to mind right now. Could go on and on. Hope this helps.