Note that if you connect to localhost, VNC will assume you have a fast link and will disable all compression. That can make things very slow if the remote host is not on a LAN with the local machine, in which case you'll have to supply the appropriate -encodings to get a semblance of speed.

Note also that with TightVNC, you can avoid the ssh -L / -encodings dance by simply saying

vncviewer -via remotehost vnctarget

Makeshifts last the longest.