Following in the "Gene, Meme, Scene, Sense" themes of the 4 main Metal Gear Solid games, the Meme expansion follows Gene and provides more maps, characters, and options to further increase the features of this game.
There are three new maps introduced in the game. The first of these is Silo Sunset - a direct translation of the nuclear silo from Metal Gear Solid: Portable Ops. It is a fairly linear outdoor map, with many winding twists and turns to maneuver in. The map is more "hemmed in" than the other urban maps available, featuring corridors and tunnels that hinder movement. The status of the base - rusting, weathered metal and crumbling concrete - adds to its historic feel. The tight quarters create a lot of intense firefights between enemy groups.
The second is Forest Firefight, a map that is, in thematic terms, a combination between two maps from MGS3's Online Mode. It combines an open, wild forest area with a small cabin that can be approached from multiple levels. Lots of sloping hills and tunnels add to the intricate nature of the level. Stylistically, the level is one of the best levels for using camouflage and concealment, and fans of MGS3 will definitely find this map a favorite.
The final map is Winter Warehouse, the only level so far to feature snow. The map consists primarily of a multi-level building - the titular warehouse - surrounded on the outside by snow. The multiple levels of the main building, as well as the tight quarters inside it, make communication very important, while the outdoor areas allow for some long-range sniper duels. Players who have invested in urban or snow camo will find an advantage here. The building itself is ruined and decrepit, and has a lot of atmosphere to it.
The other primary addition with Meme is the new unique characters. Like Meryl and Akiba from Gene, these characters can be turned on in a server and will be assigned to a random player on each team. The first of these is Liquid Ocelot, the main antagonist of MGS4. Ocelot's main skill lies in his control of SOP - the nanomachine system used by all the mercenaries in the game. His unique primary weapon is the "Guns of the Patriots" - by pointing his finger at an enemy and saying "bang", Ocelot disables that character's weapons for a short time. There is also a more powerful alternate fire that causes enemies nearby to fall into a stupor, unable to move or act. His secondary unique weapon is a single-shot high-powered pistol that can kill nearly any enemy in one bullet, but requires reloading after each shot. Ocelot is also a master of CQC - he is able to stun enemies instantly if he gets them in a hold, and his combination melee attack can also knock an enemy out more quickly than normal. Finally, many of Ocelot's distinct mannerisms are brought to the table as well - for example, rather than dodging backwards, Ocelot's animation is instead him walking backwards, his arms outstreched, laughing madly. In Sneaking Mission mode, if Ocelot is the one to find Snake, he crows out "Snake!" as he does so many times in the series.
The second new Unique Character is Mei Ling, the support character from MGS1 and Naval Captain in MGS4. As this might imply, Mei Ling can't do a lot of fighting by herself - she can only use her unique "primary weapon", and her choice of secondary weapons is limited. However, these are uniquely powerful, and thus Mei Ling is a difficult character to adapt to - but strong if you know how to play her. Mei Ling's primary weapon is a targeting marker for her battleship, the USS Missouri. While this announces her present fairly clearly - her voice rings out while she prepares the ship to fire - it's also powerful and can deliver a lot of fire in a constant barrage. Her secondary weapon - if she does not elect to take a pistol for self-defense - is a Sonar Gun that highlights enemies through walls when the gun is pointed at them. This information is conveyed to allies through the SOP network, so having Mei Ling in the background providing intelligence to the entire team is a definite bonus, if the team remembers to keep her protected.
Besides these obvious changes, there are some more subtle ones as well. The game has been patched since Gene, and changes include new skills (SOP stealth, improved SOP scanning, improved shield use), new gear (serious things like Ghillie Suits to more whimsical pieces like Crocodile Caps and Afro-type wigs), and new interface features (subtle tweaks to the Heads-up Display and score screen for ease of viewing). There's also a new game mode - Stealth Deathmatch, a free-for-all where every player is equipped with stealth camouflage and the game is to find the enemies before they find you. Finally, there's a new tournament mode on weekends - a ladder mode where teams move up in rank competing for the highest prize of reward points (spent in the shop to buy new gear).
Essentially, however, nothing has really "changed" about MGO - if you liked it before, then pick up Meme and you'll like it better. If not, it probably won't change your mind. A lot of the game's frustrations - headshots in particular - are still present, though the game has been made more beginner-friendly adjustments. For example, there are now several beginner-only lobbies, including one for Survival mode (previously, beginners were consigned to the same survival lobby as all the experienced players, resulting in newbies doing poorly and thus not getting any reward points). However, the overall domination of the game by experienced and skilled players is still heavily evident, and it can be tough to get into the game from the get-go. For current fans of the game, Meme is a must-have that adds plenty of fun new content to the game.