Not as great as the original or Opposing Force, but still a good addition to your collection.
It may be the apparent lack of connection to the original's story but, Blue Shift feels out of place and almost as if it doesn't serve much of a purpose other than to milk a little more out of the original before the sequel comes out.
That said the gameplay does fit in nicely with the previous Half-Life games. Barney, despite being only an ordinary security guard handles the same way Freeman and Shepard do. This does create an ease into the game as the player isn't learning a new set of controls or style of play.
The biggest issue with Blue Shift is its length. You can play through the game on easy in less than four hours, and on hard in 8-10 hours at best.
Blue Shift despite a few flaws does fit nicely into any gamer's Half-Life collection, including a few clever nods to the original. However do yourself a favor and make sure you've played any other Half-Life game before this one so this isn't your first taste of an outstanding series.