Players can make their own maps with the included map editor, but unlike the first StarCraft, the only way to distribute them is through Battle.net, where they are screened for objectionable content and security risks. This is very convenient, but it is more limiting than the open mapmaking tools offered with earlier Blizzard titles.
Multiplayer match types include 1v1, 2v2, 3v3, 4v4, and free-for-all. You can also set up cooperative matches against the AI.
Old School vs. New School
Many recent RTS games have de-emphasized building or eliminated it altogether to give players more time to concentrate on controlling combat units which are central to the action. StarCraft 2 hasn't taken this route, so base construction remains a big part of it, and there are no limitations to how many units you can have other than the amount of resources on the map.
The game brings the series up to date graphically and makes many improvements to the interface, but it stays quite true to the gameplay of the original. If you were expecting Wings of Liberty to revolutionize the genre, you maybe disappointed. On the other hand, if you are an old school RTS fan, you'll likely be pleased with the approach Blizzard has taken with StarCraft 2.
Starcraft has a long history as one of the most competitive RTS games available, so there are definitely some extremely skilled players on Battle.net, but Blizzard has done everything possible to ease people into the contest. You can skirmish with the AI, which is quite difficult on harder modes, until you are comfortable with the game's controls. They've provided challenge missions as well, which focus on getting you acquainted with particular units and their abilities. There is also an abundance of documentation available if you need more details. On top of all that, you are given 50 unrated practice matches on Battle.net if you want them, so there's plenty of time to learn the ropes before getting serious.
There are a lot of people playing, so once you do jump into the competitive ladders you'll find that Battle.net does a pretty good job of matching you with players of a similar skill level.
Wings of Liberty is intimately entwined with the new Battle.net. It is possible to play the single-player campaign offline, but game achievements are all tied to your Battle.net account. There is also no option for LAN play. You can have a game with friends on your network, but it will still be hosted on Battle.net, so there is no way to take advantage of the low-latency connection a LAN provides. Given that broadband Internet is widespread and LAN parties are a lot less common than they used to be, I doubt the feature will be missed that much.
The playerbase is divided by region, which makes international matches a lot more difficult. If you want to play with friends on different continents, about the only way is to buy multiple copies of the game.
The Bottom Line
While it could be that no game is perfect, StarCraft 2 certainly leaves very little to complain about. Sure, there will be some grumbling about the lack of LAN, the three-part campaign, and the centralization of mod content on Battle.net, but these don't detract significantly from the core game, which is first-rate by any standard. The single-player campaign is very robust and I suspect that people will be wrapped up in multiplayer StarCraft 2 for years to come. You'd be hard pressed to find a more finely crafted and beautifully presented RTS game.