I like PuTTY and WinSCP. They are relatively simple to use and reasonably feature rich. Unfortunately, we found PuTTY and, consequently, WinSCP to be much too slow for large file transfers and remote X Windows sessions. This is a known problem (
http://marci.blogs.balabit.com/2009/11/putty-performance.html) that remains unfixed since its last release in 2007. Our tests consistently found PuTTY to be 70% slower than alternative SSH file transfer and tunneling solutions. The slow (or halted) release cycle is also cause for concern.