I'm trying out Bilbo blogger now that I switched back to KDE 4. Before I was using Scribefire (Firefox add-on). I find Bilbo quite nice, though it still needs some polishing. One thing that I really miss is the list of all existing tags that have been already used in a blog. Scribefire has this feature and it is really convenient, because you just click which tags you want to add to a post. This is especially handy for Blogger/Blogspot which doesn't have (yet) categories.
Here's a screenshot of Scribefire's tag list.