Terrans are easily the slowest race at gathering resources, since they don't produce workers as fast as the Zerg, and unlike the Protoss the Terrans must sacrifice a worker for some time when working on a structure. Also Terran barracks take a bit longer to build than a Protoss gateway. Terrans also have poor scouting early on making them rely on defense for a while. They manage though, since they do have a few good aspects. One, their workers are stronger than the other 2 races.
Also marines produce faster than both zerglings and zealots, and have the bonus of a range attack. This allows for them to hide behind structures to make it harder for them to be attacked by melee units. Also when you enough marines, melee attackers become worthless. Terrans also benefit from repairing, making early bunkers nearly invincible. Offensively the Terrans can't really hurt a Protoss player early in the game, since zealots will shred marines. Though zerglings will die horribly to packs of marines, sunken colonies stop marines.
Once a refinery is built, the Terran's gain access to many units and upgrades. First is stim pack. This is very useful for turning marines into defensive and offensive threats. Given enough marines, stim packed marines can plow through anything, especially hydralisks. Also tanks and vultures become available, making the Terrans stronger than the other races at this point. Vultures don't work versus Zerg, however have positve effects on Terran and Protoss. Spider Mines are able to contain these two races long enough to contain them with bunkers.
They also make good scouts, since Terrans won't have any mobile detectors for some time. Tanks on the other hand is the final piece to completing a good containment. After bunkering someone down, it becomes necessary to use tanks to eliminate defensive structures, and save on units. Other races do have a hard time stopping a Terran offensive bunker once tanks become available. Though without tanks, dragoons (with range upgrade), and hydralisks can easily destroy any bunker, and once destroyed, the marines are as good as dead. However once a Terran player does get tanks, it becomes very hard for another race to break in for some time.
If bunkering failed, then it's time to expand. No race is good when spread far apart, so getting another expansion that's close is prefferable. This can easily be obtained by using bunkers and tanks to control any entrance. Also the ability of a flying command center allows for construction of a base in the safety of your base and can be moved once an adequate defense has been set up. If the Terrans manage to obtain at least 3 bases, they can just turtle up, and wait it out, since they'll have more than enough resources to create a good defense.
Even though wraiths and goliaths become available, the Terran's offense still lies in the number of siege tanks it has. Construction of many starports is not a good idea, since wraiths are very fragile, and dropships are very expensive. Terrans do benefit from having the best defense, yet in theory, they could use their defense to contain another opponent and starve them. Terrans also have poor upgrade ability because they require a science facility to reach level 2 and on for their units. As compared with the Zerg who upgrade after each transformation of the hatchery.
Once the science facility is built, all the Terran units and upgrades become available. Battle cruisers should be the first thing on your mind, since given enough resources, you can destroy an opponent with 12 battle cruisers. Nukes aren't much of choice, depending on the game. If it seems impossible to break in, then use nukes, but I must warn you that at this stage, every race has plenty of detectors, and nuking is a very long process. Terrans should be able to take out a Zerg player, as long as they've gathered 4/5 of the map. Eliminating the Zerg's spell casters with irradiate, will ensure a win, since they'll need 3 times the units to break through your siege tank / bunker defenses. The Protoss also find it hard at the end, even with advanced units to break a good siege tank line.
I find that the Terrans will be very strong on island maps now, maybe too strong. Given that they have a powerful anti-air unit, namely the goliath, this alone can hold an island from drops or assault. Battle Cruisers also rule island maps, given that they can always repair and have the yamato cannon for those tough defenses.
I can see the BW ladder being dominated by Terran island players, since the Zerg's early air is worthless against marines, and the Protoss reaver is nearly worthless with the new cool down. Once a Terran builds a factory on an island, I'm sure within a few minutes, the island will be impossible to take over given enough tanks and goliaths. Also all the new units : lurkers, dark templars, dark archons, and valkyries all become useless on an island map where most defenses are anti-air detectors
