Migrating to Linux from Windows
Practice using an Oracle VM Virtual Box and create a Ubuntu [12.04 LTS] install (use the iso from here http://www.ubuntu.com/download/desktop) on your current Windows PC and get use to the differences (some good, some not so much).
Created an 8GB VDI (Virtual Disk Image) and added the iso to the virtual disk
You can 'Try' Ubuntu or 'Install' Ubuntu - If you want to install QGIS and Postgis then your will need to use the install option.
One very good option in Oracle VM is to create Snapshots - so install ubuntu and create a snapshot in oracle vm - this way you can revert back to a clean install if your testing does not go to plan.
Settings to get ubuntu running on Oracle VM
postgis and qgis running with some sample data
The same applications are available, but the general experience will be much smoother, especially updates. Package managment is one of the key user-facing strengths of Linux. Everything you need is already packaged and only a gui or command away. No need for separate downloads or anything like that.
So install one of the buntu flavours and add the UbuntuGIS ppa to the list of sources in the software center.
First choose a distributions where you can find lots of help. Changing to an new OS is really hard transition. At the moment ubuntu seems to be the more user friendly.
Secondly learn your tools. eg. to install something on an debian system you just apt-get them.
eg for python:
sudo apt-get install python
for python's gdal binding:
sudo apt-get install python-gdal
The system will take care of any prerequisites.