I am working with these guys since last 2 and half months and I have ported around 12 books of my listed through them including few in medical and poetry.
Yesterday news letter from them to us says that they really had a good success at London Book Fair and got lot of contracts signed off on there stand.
http://www.londonbookfair.co.uk/page.../ExhibID=04652
Although I have not read through all the content on there new site
http://www.appspublisher.com/ but all they say on "Services" they really provide that all stuff, you need to check that out.
I had asked the same question about eReader which DaleDe points and its just a name of technology which all readers like stanza or iPhone kindle app uses I am not 100% sure if its no proprietary of Fictionwise or any other company.
I also personally don't agree as "reader overhead in every book" as I can clearly see a branding on each of my book title, there model helps a lot as it enables Search and listing of each book and each book gives me free SEO back links.
In a nutshell they have daily sales update for me on there control panel, I can track sales of my individual title and its because each book is listed as individual title and not through free readers, last 2 weeks my 5 books are listed in top 100 paid Apps in Medical category and I am expecting a big payout for this month
Since they have non-exclusive agreement and you can terminate agreement at any point time, i would ask you try them with few titles.
Def.