Love the size! It's thin and very light. It's also much smaller than the Nook and Kindle. I've owned two Nooks in the past (Nook Simple Touch and the Nook Glowlight) and I think the Kobo Aura's screen is comparable. I do think the light on the Nook is slightly better. The light on the Kobo Aura is a bit uneven and is more grayish at the top. However, speed when navigating and page refreshes are much better on the Kobo Aura. The touchscreen is also more responsive. I love the reading stats, but do wish that they had the lifetime reading stats I've seen available on the Kobo tablets. The main reason I switched was because of the limit Barnes & Noble puts on sideloaded content. No such restrictions on the Kobo Aura. Another minor thing is that when viewing the library, the cover images are kind of small.
Overall, I think the Kobo Aura is a nicer device than the Nook and worth the premium.