Yummy FTP has been my favorite FTP client for quite a while. I had become so used to seeing it every day that I hadn't even realized it hadn't been updated since
2007 May, 2008. That makes today a big day, as version 1.8 is out with a deluge of new features. While it still lacks the S3 support that Transmit and Interarchy have, it's solid, fast and offers all of the advanced configuration I need with a very reasonable price tag.
Highlights from the 30+ new features include an Open In Terminal command (which can set up an SSH session, log you in and
cd to the selected directory for remote folders), improved Quick Look features for local and remote previews, advanced file diffs and a greatly improved remote delete/duplicate scheme. As fast as Yummy FTP has always been for me, the idea of downloading and re-uploading a folder just to make a copy borders on insanity. I can't believe I've been doing that since 2007.
Quick tip for Yummy users: the bookmark folder in ~/Library/Preferences/Yummy FTP/Bookmarks looks (and works) great in the Dock, displayed in Folder view, especially if you organize your bookmarks hierarchically.
Yummy FTP handles FTP, FTP SSL/TLS and SFTP, and offers filtering, remote editing (with TextMate project support), auto-recovery, folder sync and more. It's available for a 30-day trial from Yummy Software, and you'll note on their site that there's a limited-time coupon ('ONLY15YUM') for a $15US license (normally $28US). That's a pretty good deal for some powerful FTP software.