I installed it because I want to have the latest release on my phone so that it will be updated in the Market when the time comes. Also, since the front camera will work in the next month or so when GB comes.
Note: This new ThunderBolt video capable version is called, simply, "Skype". If you've already installed "Skype Mobile", this will install alongside it. You should probably delete the "Skype Mobile" since it is redundant and confusing to see them both there with the same icon but different names.