Transmit is a sexy little app. Been using it since the 1.x days, it's given me the least amount of fuss of any FTP client I've used. 3.0 added a whole bunch of little goodies like tabs and more connections modes (aside from the standard FTP and SFTP). Plus, the Panic seems really eager to make a quality product. Their tech support has always been some of the most personal correspondence I've ever had with developers.

30 smackers ain't cheap, but you wouldn't be disappointed.