The campaign is 30 missions long, about 10 longer than Mech3. It's probably a little too easy for experienced Mech pilots, even on the hardest difficulty level, but it's well paced and varied in terms of terrain and goals. You begin on the moon, touch down in the arctic, make your way through forest, deserts and finally end it all in a massive city. The pace is good in that you are constantly salvaging fallen Mechs and parts as you go. Depending on how well you smash up the competition -- that is to say, how well you kill them without smashing them up too much, the better your haul is after the mission is over. This gives you access to better Mechs and better weaponry at a reasonable pace, which helps the campaign stay challenging for a longer time.
Sadly the game falls way short of Microsoft's other action combat sim, Crimson Skies, in terms of voice acting and script. Mechwarrior 4's actors are laughably bad, or at best, cringingly bland. Mission briefings feature all sorts of lame interchanges that go a long way toward showcasing a lancemate's personality but also making you long to hit the Launch button to shut them up.
Lots of people love the MechLab that has been a Mechwarrior standard for quite a while now. It's here and you'll find all sorts of color schemes, weapons, and armor types to choose from. This time your chassis isn't quite the blank slate it used to be, but you'll get an interesting Mech up and running in no time. The change primarily is that they've limited what kinds of weapons can be placed where, by adding specific hard points. If your Mech has a laser hard point at the shoulder, you've got to put a laser there. Same goes for missiles. This prevents those “all laser” Mechs that were the terror of the net at one point, and forces you to mix it up a bit more.
There are 21 different Mech types to pilot and at least as many different kinds of attack vehicles. There's something thrillingly Godzilla-like about using your weapons to swat attack helicopters out of the air and something deeply satisfying about running down a pesky APC or missile tank underfoot. It gets even better in later missions likethe ones that take place in urban city-centers.