1. install Oracle JDK 6 SE 32-bit JDK: jdk-6u25-windows-i586.exe
2. install Oracle JDK 6 SE 64-bit JDK: jdk-6u25-windows-x64.exe
3. double-click jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4.jar to launch install process.

Resulting config (Help > About > Installation Details > Configuration):

eclipse.commands=-os
win32
-ws
win32
-arch
x86
-showsplash
-launcher
C:\Users\nboldt\jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4\studio\jbdevstudio.exe
-name
Jbdevstudio
--launcher.library
C:\Users\nboldt\jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4\studio\\plugins/org.eclipse.equinox.launcher.win32.win32.x86_1.1.100.v20110502\eclipse_1406.dll
-startup
C:\Users\nboldt\jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4\studio\\plugins/org.eclipse.equinox.launcher_1.2.0.v20110502.jar
--launcher.overrideVmargs
-product
com.jboss.jbds.product.product
-vm
C:/Program Files (x86)/Java/jre6/bin\client\jvm.dll
eclipse.home.location=file:/C:/Users/nboldt/jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4/studio/
eclipse.launcher=C:\Users\nboldt\jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4\studio\jbdevstudio.exe
eclipse.launcher.name=Jbdevstudio
eclipse.p2.data.area=@config.dir/../p2/
eclipse.p2.profile=profile
eclipse.product=com.jboss.jbds.product.product
eclipse.startTime=1320007556893
eclipse.vm=C:/Program Files (x86)/Java/jre6/bin\client\jvm.dll
eclipse.vmargs=-Xms512m
-Xmx1024m
-Dosgi.bundles=reference:file:org.eclipse.equinox.simpleconfigurator_1.0.200.v20110502-1955.jar@1:start
-Dosgi.instance.area.default=@user.home/workspace
-XX:MaxPermSize=256m
-Djava.class.path=C:\Users\nboldt\jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4\studio\\plugins/org.eclipse.equinox.launcher_1.2.0.v20110502.jar
equinox.use.ds=true
file.encoding=Cp1252
file.encoding.pkg=sun.io
file.separator=\
java.awt.graphicsenv=sun.awt.Win32GraphicsEnvironment
java.awt.printerjob=sun.awt.windows.WPrinterJob
java.class.path=C:\Users\nboldt\jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4\studio\\plugins/org.eclipse.equinox.launcher_1.2.0.v20110502.jar
java.class.version=50.0
java.endorsed.dirs=C:\Program Files (x86)\Java\jre6\lib\endorsed
java.ext.dirs=C:\Program Files (x86)\Java\jre6\lib\ext;C:\Windows\Sun\Java\lib\ext
java.home=C:\Program Files (x86)\Java\jre6
java.io.tmpdir=C:\Users\nboldt\AppData\Local\Temp\
java.library.path=C:\Users\nboldt\jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4\studio;.;C:\Windows\Sun\Java\bin;C:\Windows\system32;C:\Windows;C:/Program Files (x86)/Java/jre6/bin/client;C:/Program Files (x86)/Java/jre6/bin;C:/Program Files (x86)/Java/jre6/lib/i386;C:\Program Files\Common Files\Microsoft Shared\Windows Live;C:\Program Files (x86)\Common Files\Microsoft Shared\Windows Live;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Program Files\Intel\DMIX;C:\Program Files (x86)\Common Files\Lenovo;C:\Program Files (x86)\Common Files\Ulead Systems\MPEG;C:\Program Files (x86)\Windows Live\Shared;C:\SWTOOLS\ReadyApps;C:\Program Files (x86)\Intel\Services\IPT\;C:\Program Files (x86)\Symantec\VIP Access Client\;C:\Users\nboldt\jbdevstudio-product-eap-win32-5.0.0.v201110271830R-H42-M4\studio;
java.runtime.name=Java(TM) SE Runtime Environment
java.runtime.version=1.6.0_25-b06
java.specification.name=Java Platform API Specification
java.specification.vendor=Sun Microsystems Inc.
java.specification.version=1.6
java.vendor=Sun Microsystems Inc.
java.vendor.url=http://java.sun.com/
java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport.cgi
java.version=1.6.0_25
java.vm.info=mixed mode
java.vm.name=Java HotSpot(TM) Client VM
java.vm.specification.name=Java Virtual Machine Specification
java.vm.specification.vendor=Sun Microsystems Inc.
java.vm.specification.version=1.0
java.vm.vendor=Sun Microsystems Inc.
java.vm.version=20.0-b11
line.separator=

So, the 32-bit JVM is selected automatically. 

No problem starting up, creating Example projects, etc.

Install JBDS Subclipse feature from Extras site zip.

On restart.... no problem.

So, I then installed the JBDS Mylyn feature from the update site. No problem.