I have been using Textpattern to power this site for a few months now. While Textpattern is a really great piece of blogging software, in fact it is more like a light CMS, one of its more glaring shortcoming is the lack of support for XML-RPC.
XML-RPC allows remote procedure calls to be made over the Internet, using HTTP as the transport mechanism and XML for encoding. Most of the popular server based blogging platforms such as MovableType, WordPress and b2evolution have taken advantage of the XML-RPC standard to allow remote posting using weblog clients. Using a desktop based weblog client has many advantages, including the ability to draft your post offline and to save draft copies. Without a destop based weblog client it is an extremely frustrating experience to be working on a long post and to lose everything due a browser crash just because you forgot to save frequently. I have experienced such frustration more than once using Textpattern.
The Textpattern developer community have promised to include XML-RPC functionality in the near future but so far no official stable code has been released. Fortunately all is not lost and there are plugins available which add the XML-RPC functionality to Textpattern. I recently tested one of the available plugins contributed by Kurt Raschke. After installing the plugin I tested it with a number of weblog clients, such as Qumana, Ecto, Blogjet and w.bloggar. I only managed to get the whole thing working with w.bloggar. For some reason, the other clients reported errors. W.bloggar is a solid weblog client for Windows, generously made available for free by its author Marcelo Cabral. It may be freeware but it has all the bells and whistles provided by its commercial competitors. Bloggers should definitely check out w.bloggar before forking out good money for the commercial solutions.