I'm getting it for that much now.  I have enough to keep my busy right now, but when I have little else to do sometime in the future it could come in handy, 'specially for less than 4 quid. 
 
edit: Found Yazor playing L4D yesterday and he told me then that Steam had finally provided a GBP version of their pricing.  Not only are Steam games now in pounds in the listing, but they're also now viably economical options.  As an example, TR:Underworld is currently listed at £20.69 (ordinarily, £22.99).  Nice one!