I never continued mapping, aside from experiments, but that was certainly not the editor's fault. Mouse usage is similar to Radiant, but with much better options for texture manipulation. Make sure you check out those DeadMeat tutorials on that.
The new version is recommended. It has much clearer 3D window and changing grid settings, pan and zoom is much easier. The only thing that was missing in the newer version is the option to save prefabs. A workaround is to use the old version alongside the new one to mule prefabs.
Check my posts in this topic, Trinca:
Also: on my AMD system I had to use the normal .exe instead of the 'bsp-sse2.exe' in order to see/use the green vertex manipulation handles on the brushes.
If I get back to editing on a newer pc, I'll sure be using this editor again.