The problem nowadays is that we've honestly come to expect a lot out of expansion packs. When packs like
Brood War and
The Conquerors come out, it really raises the bar of what needs to be packed in to an expansion to make it worth a purchase. The bottom line is that the
Elite Force Expansion Pack is only worth it for diehard fans of the series; none of us who enjoyed
Elite Force because it was a solid FPS first and foremost will find much to enjoy here.
There are two major parts to the Expansion Pack. The first is the addition to the single-player 'experience', the Virtual Voyager tour. This ostensibly allows you to explore the Voyager in its entirety, interacting with the crew and enjoying the time. What it ends up being is a glorified treasure hunt, as you look for action figures and talk to uncooperative crewman. Remember how everyone brushed you off in the original game? They still do now, unless they're supposed to say something for the 'plot's' sake. Urgh.
To be fair, the single-player experience picks up a bit when you get to the Holodeck, but even there it ends up being uneventful. The four 'missions' available to you range from the utterly boring (target practice) to the mildly cool (Klingon ship) to the neat-concept-bad-execution (the Captain Proton bit). Yes, black and white is cool; no, killing the same enemy over and over is not. You can tear through the 'additions' to single-player in a matter of an hour or two, and none of it approaches the brilliance of the original game.
The other core part of the Expansion Pack is the expanded multiplayer experience. There are two entirely new game modes--Action Hero, which is reminiscent of the old mod The Man With The Golden Gun. One person has all the weapons and regenerating health, and fragging them nets you five frags and the transference of the Action Hero rank to yourself. It's mildly amusing, but nothing that will keep people playing for long. The Assimilation mode is more intriguing; it's the Borg against the rest, and the Borg can teleport around the map. The other team must find and kill the Borg Queen to defeat the Borg, whereas the Borg must assimilate all of the other team. It's definitely more amusing, but still a little more gimmicky than most game's modes.
The major addition in multiplayer is the number of maps, a scad of which are for capture the flag. This is good; if I really wanted to play capture the flag, though, I'd be playing Unreal Tournament. The weapons in Elite Force just don't stack up compared to those in UT, and since the Expansion Pack makes no changes to the arsenal, that's what you're stuck with.