This post will contain a some mild spoilers about what the different single player levels are gameplay-wise. It won' spoil anything about the games story.
The Mecc singleplayer: I'm not used to playing the "realistic war first person shooter" genre, but I imagine The Mecc levels play a bit like that genre. If you rush into enemy territories with all guns blazing you might often find it hard to stay alive, if you're patient and methodical, you hardly ever have to risk your life. So basically, you decide how dangerous you want the missions to be! The very last mission is a bit different from the rest, as you have to multitask between definding a base and collecting resources. This is the only mission that you can't play at your own pace, but luckily you get to keep all buildings you have built everytime you continue after losing or dying, so you're bound to win it sooner or later.
The Reaper singleplayer: The game is quite evely split up between three different playstyles. First we have to conventional levels, which are the most common quantity-wise but might not be the ones who take up most time. Patience pays off there too. There are three of the base building levels in the Reaper story, but they're a bit easier than the Mecc ones, as you don't have to leave your base to hunt for "food" (souls from slain enemies). There are also four racing(!) level, which mayhaps are a bit tough if you don't know how to tackle them, but personally I didn't have any trouble with them. You can read my thoughts on how to beat them without any hassle in a thread with the word "frustration" in the title that I bumped five or so minutes ago before writing this post.
I've only played the first two Kabuto singleplayer levels yet, and so far I've only been close to dying once. That was when I rused right into a very heavily defended area, as I was overconfident after hardly taken any damage prior to that.
Multiplayer: I played it for a short while on a LAN party when it was new. The multiplayer is a bit like that of Command & Conquer: Renegade, Enemy Territory: Quake Wars or (the more well-known) game mode Onslaught (and to a lesser degree, Assault) in Unreal Tournament 2004/III Onslaught. I suppose the Battlefield games are a bit like that too, but I haven't played them myself. In other worlds, it's a game of bases, vehicles and teamwork!
All in all, Giants is a quirky game! But don't let this put you off, on paper might sound like all these different playstyles never can't possibly work, but trust me, they just add to the variation - all parts work on their own and the whole is even greater than the sum of the components! What also is quirky is the game's Monty Python-esque humour. If you're put off because you think all this colourfulness seems "childy", don't be. There's some really dark sarcasm behind the sugar-coated outside. ;P
Post edited March 30, 2012 by hansappel