This is mainly for information. I've been playing with the prebuild and postbuild hooks and discovered a couple of differences in behaviour between Visual Micro's implementation and the Arduino IDE implementation:
a) In the Arduino IDE, {build.source.path} gets passed as the Source DIRECTORY to any build hook, e.g. "c:\User\blah\blah\blah\Arduino\Blink".
whereas in Visual Micro {build.source.path} it is the source FILE which gets passed i.e. "c:\User\blah\blah\blah\Arduino\Blink\Blink.ino".
b) The Arduino IDE echoes any build command AND correctly redirects any output from a build hook executable to the output window, whereas Visual Micro echoes the command (twice!) but does not redirect the executable output.

A simple Batch Script (PreBuildEvent.bat) is enough to demonstrate this:

@echo off
echo %1

This is invoked from platform.local.txt
with the line:
recipe.hooks.prebuild.0.pattern="C:\Users\blah\blah\PreBuildEvent.bat" "{build.source.path}"

Neither of these are a deal breaker as I have coded around issue a) and put up with issue b)!

This is all using:
Arduino IDE v1.6.4
Visual Micro v1505.19 Sp4
Visual Studio 2013 Community
Windows 8.1

Not tried VM 1505.19 Sp6 yet but I assume there has been no changes in this area.

Sorry for the long post - hope this helps others.

Thanks for the info. Hopefully can resolve those items in the next release.

Thanks Tim, keep up the great work and unsurpassed support.

After further digging around and playing with Build Events, I took a peek inside platform.txt to see what other parameters might be useful to pass to a build event hook. Below are some of the results when invoked from VM:

{build.source.path} = "C:\Users\xxxx\Documents\blah\blah\Arduino\Blink\Blink.ino"
{build.path} = C:\Users\xxxx\AppData\Local\Temp\build1285779512254750367.tmp
{build.project_name}  = Blink.cpp
{build.board} = AVR_NANO or = AVR_UNO or = to whatever, not tested any others!
{build.arch} = AVR or some other, again not tested
{compiler.cpp.flags}  = "-c -g -Os -w -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -MMD"
{runtime.ide.version} = 10604
{build.f_cpu} = 16000000L

That's all folks, hope it is of use to some!

You can also switch on "tools>options>visual micro>compiler>show build properties" and "verbose" to see more info.

I am not sure how early the "pre" event happens. If any required properties are unavailable then pls let me know.