Congratulations on the new interface, it's fantastic. I tried the old UI for about ten minutes before going back to Bloglines, but so far I'm really impressed with the update. All the little details really add up to a great experience, particularly the keyboard shortcuts, the beautiful clean design, and the speed.
A few minor issues I'd like to raise:
1) There doesn't seem to be a good way to scroll a long post when you're advancing through posts using the j and k keys. If the post extends off the bottom of the screen, you have to take your hands from the keyboard, click the post with the mouse, and use arrow keys to read the whole post. I'd be ideal if "j" could somehow smooth-scroll through the long post when pressed again, or could jump down a certain number of lines rather than to the next post. Perhaps this is best addressed with a separate key, though.
2) I find the most common use scenario for me is to go from subscription to subscription, opening each one and scrolling through the posts. Given that skipping from sub to sub is one of the most important actions (at least from my perspective), it's a little annoying to have to hold the shift key to make it work, and to have to press one key to move to the next subscription and another to open it. Bloglines uses "s" to skip to and open the next unread subscription, which works pretty well.
3) When using the "share" feature, the default text it dumps into Gmail is pretty bad. Low signal, high noise. It just looks like a pile of marketing.
4) Occasionally the keyboard commands lose focus, or something, and none of them work.
Details I really like:
1) The "Next" bookmarklet. It took me a moment to understand what it did. This is a deceptively simple but extremely powerful idea--it blends the notification and "placeholder" features of RSS with the rich design and individual character of a web page. Plus, the sites you like get to keep their ad revenue.
2) Starring and tagging functionality, while non-revolutionary, is very cleanly implemented and easy to use.
3) Overlays (when refreshing, etc) are a nice touch.
4) The subscription selector is mind-blowingly awesome, both in terms of UI and usefulness.