Building on Alex's answer, I used RegEx to read the AssemblyVersion (and other information) and use that in my WiX/MSI filename and version strings. Hopefully my answer isn't too noisy.
Here is the top of my .wixproj file. Points of interest are the first PropertyGroup, OutputName, and DefineConstants:
<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<In>$([System.IO.File]::ReadAllText('$(MSBuildProjectDirectory)\..\MyApplication\Properties\AssemblyInfoCommon.cs'))</In>
<Pattern>^\s*\[assembly: AssemblyVersion\(\D*(\d+)\.(\d+)\.(\d+)</Pattern>
<AssemblyVersionMajor>$([System.Text.RegularExpressions.Regex]::Match($(In), $(Pattern), System.Text.RegularExpressions.RegexOptions.Multiline).Groups[1].Value)</AssemblyVersionMajor>
<AssemblyVersionMinor>$([System.Text.RegularExpressions.Regex]::Match($(In), $(Pattern), System.Text.RegularExpressions.RegexOptions.Multiline).Groups[2].Value)</AssemblyVersionMinor>
<AssemblyVersionBuild>$([System.Text.RegularExpressions.Regex]::Match($(In), $(Pattern), System.Text.RegularExpressions.RegexOptions.Multiline).Groups[3].Value)</AssemblyVersionBuild>
<Pattern>^\s*\[assembly: AssemblyDescription\(\s*"([^"]+)"</Pattern>
<AssemblyDescription>$([System.Text.RegularExpressions.Regex]::Match($(In), $(Pattern), System.Text.RegularExpressions.RegexOptions.Multiline).Groups[1].Value)</AssemblyDescription>
<Pattern>^\s*\[assembly: AssemblyProduct\(\s*"([^"]+)"</Pattern>
<AssemblyProduct>$([System.Text.RegularExpressions.Regex]::Match($(In), $(Pattern), System.Text.RegularExpressions.RegexOptions.Multiline).Groups[1].Value)</AssemblyProduct>
<Pattern>^\s*\[assembly: AssemblyCompany\(\s*"([^"]+)"</Pattern>
<AssemblyCompany>$([System.Text.RegularExpressions.Regex]::Match($(In), $(Pattern), System.Text.RegularExpressions.RegexOptions.Multiline).Groups[1].Value)</AssemblyCompany>
</PropertyGroup>
<PropertyGroup>
<Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
<Platform Condition=" '$(Platform)' == '' ">x86</Platform>
<ProductVersion>3.7</ProductVersion>
<ProjectGuid>MYGUID00-840B-4055-8251-F2B83BC5DBB9</ProjectGuid>
<SchemaVersion>2.0</SchemaVersion>
<OutputName>$(AssemblyProduct)-$(AssemblyVersionMajor).$(AssemblyVersionMinor).$(AssemblyVersionBuild)</OutputName>
<OutputType>Package</OutputType>
<WixTargetsPath Condition=" '$(WixTargetsPath)' == '' AND '$(MSBuildExtensionsPath32)' != '' ">$(MSBuildExtensionsPath32)\Microsoft\WiX\v3.x\Wix.targets</WixTargetsPath>
<WixTargetsPath Condition=" '$(WixTargetsPath)' == '' ">$(MSBuildExtensionsPath)\Microsoft\WiX\v3.x\Wix.targets</WixTargetsPath>
</PropertyGroup>
<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x86' ">
<OutputPath>bin\$(Configuration)\</OutputPath>
<IntermediateOutputPath>obj\$(Configuration)\</IntermediateOutputPath>
<DefineConstants>Debug;AssemblyVersionMajor=$(AssemblyVersionMajor);AssemblyVersionMinor=$(AssemblyVersionMinor);AssemblyVersionBuild=$(AssemblyVersionBuild);AssemblyDescription=$(AssemblyDescription);AssemblyProduct=$(AssemblyProduct);AssemblyCompany=$(AssemblyCompany)</DefineConstants>
<SuppressValidation>False</SuppressValidation>
</PropertyGroup>
<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|x86' ">
<OutputPath>bin\$(Configuration)\</OutputPath>
<IntermediateOutputPath>obj\$(Configuration)\</IntermediateOutputPath>
<DefineConstants>AssemblyVersionMajor=$(AssemblyVersionMajor);AssemblyVersionMinor=$(AssemblyVersionMinor);AssemblyVersionBuild=$(AssemblyVersionBuild);AssemblyDescription=$(AssemblyDescription);AssemblyProduct=$(AssemblyProduct);AssemblyCompany=$(AssemblyCompany)</DefineConstants>
</PropertyGroup>
And then in a .wxi file I have this:
<?define MajorVersion="$(var.AssemblyVersionMajor)" ?>
<?define MinorVersion="$(var.AssemblyVersionMinor)" ?>
<?define BuildVersion="$(var.AssemblyVersionBuild)" ?>
<?define VersionNumber="$(var.MajorVersion).$(var.MinorVersion).$(var.BuildVersion)" ?>
And finally in my Product.wxs:
<?include Definitions.wxi ?>
<Product Id="$(var.GuidProduct)" Name="$(var.AssemblyProduct) $(var.VersionNumber)" Language="!(loc.LANG)"
Version="$(var.VersionNumber)" Manufacturer="$(var.AssemblyCompany)" UpgradeCode="$(var.GuidUpgrade)">
<Package Id="$(var.GuidPackage)" InstallerVersion="301" Compressed="yes" InstallScope="perMachine"
Keywords="!(loc.Keywords)" Description="$(var.AssemblyProduct)" Comments="$(var.AssemblyDescription)" />