Lets break it down... 5 games for 15 pounds, thats a mere 3 pounds per game! Half Life 2 was a highly anticipated title on the pc and to have it on the xbox360 is great. The only thing it lacks is rich up to date graphics but that is a minor complaint. The gameplay more than makes up for this.
Portal was being sold on XBLA not long back for 10 pounds on its own. This is where the pack comes into its own rather than just be a cobbled together collection/rehash.
Portal allows you to mess with gravity through the use of a gravity gun. The idea being that you have to escape from a maximum security research centre.
Achievement wise you will be playing this game for a good 6 months to get a full 1000g, i have never seen anyones card have it (apparently you are a god if you do have the score).
All in all i cannot praise this release enough, like i said in the title...even a fool would buy this!