As I've previously discussed, I've recently moved from Bloglines to Google Reader. So far, I'm loving it - the 'share' feature alone is great (and will be better the more of my acquaintances use the site... hint...hint...). As well as appearing on murky.org's homepage (as I type), my shared links are available here, as well as within your own Reader account, if I'm one of your contacts. Heather Hopkins has done an analysis of the two sites. Bloglines is ahead of Google Reader (but I seem to recall that it did have a head start). Interestingly, users of Google Reader tend to read much more news, and users of Bloglines tend to view much more photography.
What's interesting to me is how (with a little wobble) the sites have tended to move up and down together, one isn't pulling ahead of the other, despite how bloglines decided to (factually) spin it by pointing out they were ahead.
I've used Reader for about a week now. Long enough to get the feel, not long enough to be locked in. The ideal time to make a judgement.
Bloglines somehow feels, to me, a little more developed. One can keep items unread (though google has the 'star') (UPDATE: This is actually wrong, there is an unread feature in reader - thanks Aq) and the feeds are sorted by feed. In Google Reader the feeds seem to be arranged chronologically, which isn't always desirable (I'd want to sort oldest first, or by feed with oldest first) (Update: I had a blind spot, you can change the sortorder).
The general interface for reader is just slick. You can select one feed at a time, but I just hit 'all items' and scroll with the mouse wheel. As items are displayed they're marked as read (you can scroll up if something zoomed past too fast). Hitting the 'star' marks the item as something you want to look at later. Hitting 'share' will do the obvious of sharing it with your contacts (who use reader) as well as adding it to a webpage.
When they first implemented 'share' they got it very wrong indeed, everything was shared. Bad, bad idea. What happens now is that one manually clicks 'share'. Each feed can be 'tagged', I have tags like 'cycling', 'comics', 'rugby' and 'science'. You can make it so that everything in a given tag is shared (my tags are all private). I don't see any need to do this - if someone wants everything in a feed they can subscribe themselves! The sharing feature, right now, is pretty damned good - and it works 'as expected', which is about the best that any software feature can expect.
Instead of 'sharing' (for public consumption), one can 'star' (to make it easier to find something later). It is so easy to 'star' something - very easy. So easy that one can end up with loads of items to read 'later' (I'm starring something for more considered perusal)... but then, it's very quick to scroll the starred items - and of course, there is a top notch search function. (There are keyboard shortcuts)
I've only found one problem with reader. That is occasionally it will say there is one new article, but refreshing everything doesn't reveal it. This is a weird bug, but wait a bit and it generally clears as other articles come in.
The other issue is pretty minor. It's the stats. There are a whole load of metrics which help you to pick out the feeds you read all the time, and those which you always miss. These seem to be based on if a feed is displayed (so I tend to read 100% of items as I view all items and scroll) - I'd much rather have a list based on how long each item was on screen for. For example, I scroll through slashdot pretty fast, stopping occasionally, but I will tend to linger over sites like xkcd and Bike Noob, I will click through to sites like Yehuda Moon. Stats based on clicks and time on screen would be much more useful to me than simply the fact that an article has been on screen for a few seconds.
Bloglines does share some of this, but on the whole, I think I'm a Google Reader convert. I did look at it once before - and moved back. This time, I gave it a chance and I'm staying. There's something about the way it's put together which is really nice - now, if only more of my friends were using it to 'share'....
.... and it's been built with the blind in mind too, that's got to be a good thing.
Of course, this site's feeds are easy to access: