Everybody says it's great but, as for me, it froze my 2-months-old laptop and slowed it down to near stillness; I had to uninstall it to have the system work normally.
My suggestion is STAY FAR FROM FILEZILLA!!!!
As for what I use, CuteFTP-Pro; been using it for the last 2-3 years, it never had the tiniest glitch.
My alternative is Ipswitch WS_FTP, coming with a free version called WS_FTP LE.
Third option is CooffeeCup DirectFTP: very good, very easy, very cheap - with a free version, too.
Other fully free clients (no paid version) are the following.
ClassicFTP (my favorite free FTP);
FreshFTP (very good, very easy, very lightweight);
FileZilla is by far the best FTP client, as it has many features like drag and drop, multiple tabs, built in local file browser, path listing, coded commands, transfer queue, etc.
For Mac, I use Cyberduck since it's a lovely simple FTP program for dragging and dropping folders into the little application. It stores all of the FTP connections for future use, and easy to use with a built in queue and other features.