a) Minimal layout means more info on the screen at once.

b) High signal-to-noise ratio in submissions and in comments, since user rankings of them affect both.

It may degrade with time… I can already think of several fairly significant ways to game the system and get a lot of karma quickly. But for now, I’m pretty sure it’s the best out there.

First impressions are important, so here are mine:

-Banner add at top annoying (hope it goes away if you sign up)
-Tag cloud distracting (useless to me as I don’t use them, and I see it only useful for casual browsing)
-Some graphic problems (missing files)
-Only 1/6 of my initial loaded page is news (4 entries, compared to 18 on Reddit and Digg (initially 4) you can shrink text to see more)
-Navigation poor, only can visit ajacent pages, no jumping, not very versitile
-News refresh only in section, but resets vertical displacement either way so redundant.
-Main features are offered everywhere, nothing unique. I can subscribe to RSS feeds of my friends bookmarks or to a tag group on Del.icio.us, Digg, Reddit, so why use BlinkList?
-To me, seems to be marketed to beginning social bookmarkers. I fear that your user base may evolve and you might lose them unless you come out with some defining feature

If you have any other questions, feel free to ask. I plan on trying it out after work on Firefox, and critiquing it a little more. Overall, I can’t see myself using this service.