Mechwarrior 4 Mercenaries isn't so much a sequel as it offers a new facet of the Mechwarrior universe, as well a broader sense of the Fed-Com Civil War.
In this game you are a Mercenary, a hired gun who works for the highest bidder. No matter which side they're on.
You are the Chairman of the Board, the CEO of your band of mercenaries. This brings with it several elements that make the game different every time you play. Including in this is the ability within the game to visit the Free Market, where you can Hire and/or Fire new mech pilots, as well as buy and or sell new mech chassis and additional weapons.
Another task for you is to choose which organization who will sponsor you. Each organization, much like the real corporate world, will give you unique advantages. No two organizations will give you the same advantages. The Northwind Highlanders' brand name recognition carries high honor, and with it, high paychecks. The other sponsors will give you access to more money to start, or early access to coveted Clan weapons. Choose the Kell Hounds if you don't want any advantages or special favors.
On every planet you go to, you will have a choice of missions. Some missions you have to play first before you can play others. But choose certain missions over others and you will find yourself suspect.
If you found fighting on only one planet in the original Vengeance boring, your taste for travel will be satisfied in Mercenaries, for as a mercenary the money is where the jobs are, and it doesn't matter who's paying (at first). Many different planets will be on your port of call list, and many different types of terrain will be encountered.
Also, while the original game Vengeance was quite progressive, this game is not as progressive, although you do start off with light mechs at first, and fight on a cold planet where heat sinks are super-efficient.
In a first in Mechwarrior, you can get heavier chassis by either battlefield salvage, or by buying or selling mech chassis in the Free Market.
This game has another historic first in the Battletech universe. In some missions, you will lead not one, but TWO lances. Yes, you will have up to seven fellow mech warriors to lead and it does get hairy in the later missions.
There is only one aspect to the game that I had a hard time getting used to. Those of you who have played previous versions of this game will remember that in the Mech Lab, you could customize your mech to carry certain types of weapons over others, in spite what weapons the mech originally carried.
But in Mercenaries, as in Vengeance, such is not the case. Each battlemch chassis, depending on its original default load out, has slots that will "only" take the type of weapon that was loaded. Energy weapon slots will only take energy weapons, and so on. Its only a small complaint, because, as you will see, there are many different weapons to choose from, including several new types of weapons. Also, you will be able to customize more than the weapons - the camo scheme, the engine, type and thickness of armor, and even optional equipment are all up to you.
As for the missions themselves, players of MW4 Vengeance will notice a few changes, mostly cosmetic, in the HUD. The damage display indicator, both of enemies and your own mech, will be more detailed, and your targeting reticle will be slightly different.
The only thing I didn't like in Mercenaries was the departure from video briefings, to be replaced with a simple audio briefing. It seemed very sterile to me, anyway.
Overall this is a very solid entry into the Mechwarrior universe.
For anyone who is warily eyeing an upgrade to Windows 7 or buying an entirely new computer, I recently purchased a new pc with Windows 7 on it, and Mercenaries runs just fine on it, which was a pleasant surprise, because I remember buying a new computer with Windows 98 on it, and being most disappointed that I could not run MW3 on it.