• PDFs do not reflow, so you are stuck with the page format / aspect ratio / proportions that the pdf brings with it.
• Margins can occupy the most of the page - even if it has margins on 2 sides which if eliminated would rescale the text to a legible size kobo does not.
• Scaling is not granular enough - 100, 125, 150, 175, 200 - I'd like scaling by 5% not 25%
• When scaled, next page and previous page actions disappear - instead you move inside the scaled viewport - again, poor margin management, as margins do not count - kobo should work the text not the page (text+margins) - Next page and Prev page should always be available - maybe central button should switch between page mode and viewport move mode.
• When scaled, the page is positioned odd, again, no way to actually position around text not margins+text.

All this makes pdfs on the kobo a hit or miss - I've found pdfs that look readable and pdfs that are completely unreadable (font too small to read) - text is 30% of surface, rest is occupied by empty margins. There's always the choice to convert those pdfs to epub with calibra which will allow them to reflow, ie text size can be controlled. However, even that could be a hit or miss proposition, as certain styles in the pdf convert poorly.

Overall, I find the kobo a worthwhile device. Having read books on various pocket pcs and the iphone, I can handle small fonts and quirks of display. the epaper is indeed very nice, reading on the kobo is not tiring on the eyes. Also, completely legible outside under the sun.

Other things about the kobo:

• It sucks I can't just put files on the device using explorer. I can see both the card and the memory as drives when the kobo is connected, but I can't just drag files there, I have to use Adobe Manages crap to transfer.
• When I unboxed the device, it had a film over the screen and some text on that film. At least that's how it appeared; that the film had the text printed on it. Surprise! After taking down the film, the text is on the screen, it was the last page displayed on the device... and it remained active until I unboxed the device. Checking the battery, showed >50% battery life, even with this page being displayed on the device since production. WOW! It's very strange to see anything on the screen when the device is sleeping also; you have the impression that this text drains the battery, but it's not. changing pages and the device cpu is what drains the battery, not keeping the screen alive.
• There's some ghosting from the start page: I can faintly see a "Welcome to your kobo ereader" under every page. It'll probably go away at some point.

The "unreadable" one - notice the margins that occupy at least 50% of both the width and the height of the page.

The "readable" one - the margins are smaller, which makes text size decent (trust me) to read. Of course, if it actually filled the page vertically, that extra 15% would've made it even better.

The "stupid" one - it's a pdf with images in it (scans) of pages. I call it the stupid one cause it's the worst type of pdf there is. However it was readable due to the aspect of the page somewhat matching the kobo screen.

And now a .lit converted to epub - when the epub is nicely formatted, this is the perfect reading experience.

EDIT: All above images were done with "Whole Page" option. A good option is scaling 100% which will "fit-horizontal". It's basically what I have set as default now.