Doesn't appear to have a way to edit the date / time of individual RSS posts, which is a dealbreaker for me. No built-in FTP / SFTP publishing either. UI is a bit rough with typos and seems to force itself to fullscreen, at least on my machine? Also no HiDPI support, so the UI is a bit blurry on hi-res Windows 10 machines.
But it's very lightweight in terms of resources, and you can hand-edit the HTML code manually if you type into the "Preview" window. No way to choose your favorite monospaced font for the code editor though.
Probably can't expect too much from a freeware app, but it could've been really useful with some more polish and more features.