Starting with gaming, it depends on what type of gaming you want. If you're happy with the cutesy style of the Wii and enjoy the sort of family games it provides, then most of the PS3 games won't really float your boat. However, if you want some more serious games with considerably better graphics and better online interactivity then the PS3 will be more suitable.
The 80GB hard drive is used for saving stuff on from game saves, demos downloaded from the Playstation Network, old Sony games you can download, any music, photos and videos you want to put on there as well. A lot of the games need an update file to start with so that account for some of the space as well. 80GB should be more than enough though.
I've just bought one last week mainly for the Blu-Ray player. The difference between a Blu-Ray film and a standard DVD is amazing. Obviously, you need to already have an HDTV otherwise it's a waste of time unless you plan to upgrade soonish..
The only thing I'm not a huge fan of is the controller and the system interface. I prefer my 360 controllers and the accessing of system data and online stuff is much easier on the 360, although that could partly be because I'm used to it. Also, the PS3 does not come with an HDMI lead so you'd need to pick one of them up as well. Ignore the official Sony one that shops will try and flog you and pick one up from Argos or Tesco.