YummyFTP is a very complete commercial FTP and SFTP client. According to the developers, it was built by Mac devotees so that it can be used both by novice and advanced users.
There are tons of features available; that is for sure. I will describe the most important ones for me. As I always say, you need an application that you feel comfortable with and which has the features that suit your needs. In my case, I always look for a client that can connect to different types of servers. This one supports FTP, SFTP and FTPs. That is really all I need in terms of protocol support. It has a nice site manager, which allows you to add as many sites as you want and type in all their details so you don't need to do it again. FTP aliases are one interesting and very useful feature. This allows you to upload data to a server by dragging and dropping files or folders on your Mac to an icon on your desktop, or any other location. This saves a lot of time. Lastly, I like the Automatic Failure Recovery feature. If there is a disconnection when you are sending or receiving data, YummyFTP will reconnect until the files are successfully sent.
There are many other interesting features. For a full list, visit the developer's website. They explain everything to them quite well.
In my testing, YummyFTP worked fine with a few different FTP servers. The listing of folders was quick and transferring files didn't present any problems.
Quite useful application for FTP usage.