1) The lack of "go-to" functionality is problematic, as your last position is not remembered if the app crashes, resets or if the battery goes dead while you are reading. Mix this with books that aren't properly divided into chapters (I remember the preloaded Darwin "Origin of Species" as having all its 900+ content pages listed to the one final chapter) and the lack of any provision to auto-insert chapter breaks every fifty pages or so if they're not there makes "pick up where you got lost" impossible until this particular beast evolves for a few more millenia or more. Even use of the Firefox sqlite extension (which can view/edit .kobo/KoboReader.sqlite directly) isn't an easy way to set bookmarks back to a specified position - it wants chapter name, paragraph number and word number in that paragraph to be in the "content" table, not just "go to 25% because that's where I lost my place and gave up".
2) External SD/SDHC support is badly broken. Writes from a USB-connected desktop PC to an SDHC card inserted in the Kobo's top slot often fail with unexplained
disk write errors, even where placing the same card into a standard PC SD/SDHC card reader would've worked properly. Furthermore, the "Kobo is processing new content" - already an incredibly slow operation - will fail and go into an endless reset loop upon encountering even one damaged *.epub file on the card. It provides no indication of what's wrong or which file is causing it to fail.
3) The use of one huge *.sqlite database on the internal microSD/SDHC card to hold seemingly everything is not a solution which will scale well. Calibre can download directly to "Card A" (subject to bugs listed above) as it's copying proper *.epub files to the file system; the same is not true of Kobo's own app and (I suspect) ADE, which rely on dumping everything to .kobo/KoboReader.sqlite or .kobo/kepub/* in some incomprehensible format. That the *.sqlite file ends up as a list of every chapter of every book on the device, plus a list of what's on any external SD cards, could allow it to grow to a huge size which makes an already-slow device even slower. Even *.epub files which have been manually deleted from internal memory remain in the book list (unless removed by tools such as Calibre), giving only a "this content is locked" bogus-DRM error because the device isn't smart enough to either remove orphan database entries or properly report "404" if the *.epub is not found.
4) The handling of any damaged *.epub files on the
internal microSDHC card, while not quite as broken as that for the externally-inserted cards, still leaves much to be desired. Upon finding one damaged file (regardless of card size), the search silently ends without even looking at any subsequent *.epub's on the device. Download a thousand free books and a few hundred appear... good luck trying to determine which of the first volumes to be on the file system and not on the list of books in Calibre/on the device could be the problem file?
5) The "processing new content" should be something which can happen in the background while one is reading, instead of rendering the device inaccessible to anyone until the scan completes.
6) The list of books looks like something out of a DOS 1.0 flat-file system; this lack of ability to categories volumes into folders or separate collections might've made sense if there were only a floppy disc's worth of storage on the device, but on a 16GB card with several thousand books this will become unwieldly rather soon. Even the "hide preloaded books" functionality which was added to the original Kobo remains missing from the wi-fi version, despite this unit's support for larger cards.
7) It is possible to cause the reader to reboot simply by attempting to read a document with large, overly-complex HTML tables such as the list of main articles by category in even a very-abridged
Wikipedia collection. Like with the "processing new content" on the external card, rebooting without explanation is not the suitable user-friendly response to something the app can't handle properly.
8) The approach of "synchronisation" (where deleting content from the device affects the Kobo desktop app, or vice-versa) needs to be scrapped. Given the limitations of the "flat file system" approach to listing titles and the space limits imposed by not using the broken external SDHC card support, it makes more sense to use the desktop PC and its under $100/terabyte hard disk storage capacity to store every book a user has ever owned, while copying just the ones actually being read to the device. Effectively, the PC should be a full archive, not a mirror of what little is on the device. Calibre handles this well (and can be trusted not to go "1984" with deletions of device content just because the same book is missing on an upstream provider) but Kobo's own app does not.
9) Support for both Linux and Win2000 is incomplete and what little is supported is not documented. Any attempt to contact 'kobobooks.com' to ask whether the device is even usable under either of these gets a blunt 'no' (the actual situation is that ADE has no Linux version, while Kobo.exe and Calibre have no Win2000 support - but to say nothing works is a bit much).
10) The handling of books acquired from multiple sources is kludgy at best. There shouldn't be three different apps needed on the desktop (Kobo.exe for books purchased from Kobo itself, ADE for library books, Calibre for free *.epubs such as Gutenberg and Feedbooks...) just to manage one simple device.
11) The 100 preloaded "free books" appear to be in some oddball DRM format when simple, unencrypted *.epub files would offer more flexibility. A DRM-free bundle could be easily transferred to Calibre, archived on the desktop, and only the ones actually in use could remain on the device. The use of draconian restrictions management on what is clearly public-domain content effectively constrains Calibre from doing anything with this collection other than the removal of individual volumes. The only ways to restore individual books appear to be either a factory reset (which wipes everything on the FAT32 partition, replacing just the 100-book preloaded bundle) or a visit to legitimate public-domain sites such as Gutenberg to get clean, non DRM-infested *.epub's of this content which can be archived freely at will.
12) The wi-fi web browser functionality is of limited use if it's locked to only one website. While it is possible to create an *.epub book which, like a standard webpage, is packed with both internal and external hyperlinks (not to mention Wikipedia by name...) there is no means to use the internal browser to follow any of these links. Kobo turns *.epub from hypertext to flat plaintext, despite a crude browser and a wi-fi connection being available.