I took another look at the current dev. build of Flock, and it's definitely getting closer to a final release. The quality is noticably better than previous builds - I don't get the spinning beachball of memory thrashing hell I got before.
There is only one nit I have left to pick with Flock. It's got the best rich text editor of all of the standalone blog posting apps I've tried (and I've tried a LOT) - except for the lack of an ability to sort and/or filter categories for application to a post before publishing.
I have a LOT of categories on my blog - I use them more like tags than full-blown taxonomic categories - so reading through an apparently unsorted list of 300 tags can take much longer than writing the post took in the first place.
Once that's taken care of, I can totally see myself living in Flock. I'm loving the Flickr integration, and the del.icio.us tie-in, and lots of other refinements. Great job, so far!