If you run Debian 6 (Squeeze) under an VMware Hypervisor (ESXi 5.0+) with VMware Tools installed and you want to upgrade to Debian 7 (Wheezy) make sure you uninstall VMware tools in advance.
Several machines did not boot up after the upgrade with the 3.2.x kernel and hanged forever just after “Switching to guest configuration”. I always create snapshots in advance of major upgrades. So there was no data loss, however, the whole upgrade process had to be restarted…
Hint: Starting with Debian 7 open-vm-tools are included in the official Debian repository: This package is an open source replacement for VMware tools and fits perfectly into the Debian system (e.g. post kernel update triggers). IIRC the open-vm-tools package is also included in the official Ubuntu repository (12.04 LTS has a recent version) – there is also an old version in 10.04 LTS included, however, I never tested that. VMware hypervisor detects it as a “third party”/”manually maintained” VMware tools package and provides the usual options.
Update 2013-09-25: I’m using open-vm-tools since May and had no problems so far.