I had a N905, and the 2.6.1 version updated automatically. then - the problems begun. Especially the books on the SD-card hadn't been recognised any more. But at last, the whole system became confused, and I had to send the device in. I received another N905 in return, with the 2.5.2 version. I asked the Kobo guys and they said there is another update at work, but they cannot say when it is to be released. Due to my experiences, I would not recommend to update anything manually. Allt he more that 2.5.2 runs (almost) without difficulties.