What is vhlt

If you are keeping up with the level design news for goldsrc, you may have heard of vhlt.
Vhlt is a new set of compiler which are generally better than zhlt. They actually are a fork of the zhlt project so you can use most of the command line switches of zhlt with vhlt.

Origins of vhlt

vhlt (vluzacn half life compile tools) were originally distributed over this sven coop thread. There, you can see the different versions of the tools.
Right now, the latest version is v31

Advantages of vhlt

vhlt adds a lot to the mix but mainly it is useful for the func_detail. This entity behaves like a func_wall except that it also generated shadows thus behaving like a normal solid.
Other useful changes includes the -blur command line switch which diffuses the shadows and other visuals changes like better shading, better lighting and shadows.

Conclusions

So should you use vhlt?
I would say yes because they are quite mature at this stage and there is no real advantage in using zhlt right now.
Installation is simple, just download and replace the compiler tools like csg.exe, etc from zhlt to vhlt. You will also need to add the wad paths. Follow the readme.txt given with vhlt and you should be fine.
Note : vhlt treats missing textures as errors and won't compile. Just keep that in mind.