Blue Shift? They might as well have called it Green Shift because it's going to be shifting a lot of green notes into the waiting hands of Sierra, Valve and Gearbox. They could print the words "Half-Life" on sheets of toilet paper and they would sell like hotcakes. Still, conveniently enough there are reviewers like me around to tell you if it's actually worth buying (Blue Shift, not the toilet paper). So is it? Well, to get to the point right away, no, not yet anyway.
The game isn't bad, there just isn't enough of an actual game in there. Whereas Opposing Force offered new weapons and new enemies, Blue Shift offers neither, and the "same setting, different player character" idea is also now less of a novelty. This time you play Barney Calhoun, one of the many security guards in the Black Mesa complex. You'll catch glimpses of Freeman, just as Adrian Shepard did in Opposing Force, but briefly seeing Freeman wearing a tie rather than a Hazard Suit is hardly reason enough to pick up the add-on. The insult added to these injuries is the brevity of Blue Shift - it took me less than four hours to complete, and that included getting stuck twice and having a quick food break.
Those four hours weren't exactly wasted, far from it - Gearbox have again done an excellent job on the levels and the new, higher detail character and weapon models mean it doesn't look quite as dated as it could have, not to mention the still unsurpassed AI of the enemy soldiers. But four hours is just far too short, even for an addon pack. Granted, it doesn't cost much, and as well as the high detail models and new single player mission you get Opposing Force CTF (and lucky American gamers get Opposing Force in its entirety). But if you've already got Opposing Force all you'll really be buying Blue Shift for is the single player, and you'll be through with that in an evening. Try thinking of it as 4 pounds (or six dollars) for each hour of gameplay. Value for money? Hardly. Wait for the price to at least halve before grabbing it.
Bottom Line: Blue Shift is all about quality and not quantity. It's only worth getting if you seriously think you can justify spending so much for so little, and even as a big fan of the original (hey, who isn't?), I can't make such a justification at that price.