After adding

http://download.jboss.org/jbosstools/updates/JBossTools-4.0.0.Alpha2.core/

to available update sites:

• Not able to update via 'Check for updates' (Help - Check for updates)

  Cannot complete the install because one or more required items could not be found.
    Software being installed: JBoss JAX-RS Tools 1.4.0.Alpha2-v20120922-0406-B33 (org.jboss.tools.ws.jaxrs.feature.feature.group 1.4.0.Alpha2-v20120922-0406-B33)
    Missing requirement: JBoss JAX-RS Tooling (Core) 1.4.0.Alpha2-v20120922-0406-B33 (org.jboss.tools.ws.jaxrs.core 1.4.0.Alpha2-v20120922-0406-B33) requires 'bundle org.eclipse.wst.sse.core 1.1.701' but it could not be found
    Cannot satisfy dependency:
      From: JBoss JAX-RS Tools 1.4.0.Alpha2-v20120922-0406-B33 (org.jboss.tools.ws.jaxrs.feature.feature.group 1.4.0.Alpha2-v20120922-0406-B33)
      To: org.jboss.tools.ws.jaxrs.core [1.4.0.Alpha2-v20120922-0406-B33]
  

• Not able to update none of the components via 'Install new software' using the Alpha2 update site. E.g.

  our original request has been modified.
    "JBoss Tools EGit Integration (Experimental)" is already installed, so an update will be performed instead.
    "JBoss OpenShift Tools" is already installed, so an update will be performed instead.
  Cannot complete the install because of a conflicting dependency.
    Software being installed: JBoss Tools EGit Integration (Experimental) 2.4.0.Alpha2-v20120922-0402-B32 (org.jboss.tools.openshift.egit.integration.feature.feature.group 2.4.0.Alpha2-v20120922-0402-B32)
    Software currently installed: org.jboss.tools.openshift.egit.integration.feature.source.feature.group 2.4.0.Alpha1-v20120910-1041-H30
    Only one of the following can be installed at once: 
      EGit integration UI 2.4.0.Alpha1-v20120910-1041-H30 (org.jboss.tools.openshift.egit.ui 2.4.0.Alpha1-v20120910-1041-H30)
      EGit integration UI 2.4.0.Alpha1-v20120908-0237-H23 (org.jboss.tools.openshift.egit.ui 2.4.0.Alpha1-v20120908-0237-H23)
      EGit integration UI 2.4.0.Alpha2-v20120922-0402-B32 (org.jboss.tools.openshift.egit.ui 2.4.0.Alpha2-v20120922-0402-B32)
    Cannot satisfy dependency:
      From: JBoss Tools EGit Integration (Experimental) 2.4.0.Alpha1-v20120910-1041-H30 (org.jboss.tools.openshift.egit.integration.feature.feature.group 2.4.0.Alpha1-v20120910-1041-H30)
      To: org.jboss.tools.openshift.egit.ui [2.4.0.Alpha1-v20120910-1041-H30]
    Cannot satisfy dependency:
      From: JBoss Tools EGit Integration (Experimental) 2.4.0.Alpha2-v20120922-0402-B32 (org.jboss.tools.openshift.egit.integration.feature.feature.group 2.4.0.Alpha2-v20120922-0402-B32)
      To: org.jboss.tools.openshift.egit.ui [2.4.0.Alpha2-v20120922-0402-B32]
    Cannot satisfy dependency:
      From: org.jboss.tools.openshift.egit.integration.feature.source.feature.group 2.4.0.Alpha1-v20120910-1041-H30
      To: org.jboss.tools.openshift.egit.integration.feature.feature.group [2.4.0.Alpha1-v20120910-1041-H30]