If anyone hasn't upgraded their HDD then I strongly recommend they do. I now have 320GB HDD which cost £40 and literally took 2mins to install. Here are some tips if your planning on buying a HDD.
1. Must be a internal 2.5" Sata drive 5400rpm.
2. Phone Sony for a spare Caddie HDD, this is free of charge and worth having as a back up.
3. Do not over tighten screws (hence point No2), Use Philips PH1 screwdriver.
4. Back up gamesaves before you swap HDD.
5. Don't worry about operating system, once you swap HDD everything remains the same on the PS3 because the operating system is stored in the memory and not the HDD.
This is a very simple procedure that Sony actually encourages and doesn't void your warrantee.