For a long time I've been using TightVNC as my VNC remote desktop solution.  I don't remember why I favored it over RealVNC, I think it was because it seemed more responsive and has a great selection of compression options for slow networks.  But all this time I've been hoping for a VNC client that supports multiple monitors, and RealVNC has been providing this already for ages.

I'm now using RealVNC 4 Free Edition and in addition to it supporting my dual-screen PC's both at home and at work (you needs to stretch the VNC window to display it all) it also detects your connection speed and auto selects the colour depth.  So when remote controlling a PC on my LAN I get full colour depth, whilst remote controlling a PC over the Internet I get reduced colours depth automatically.

For reference, TightVNC has multiple-monitor support coming, and is available now in the development version (1.3.8).