The three Space Marine heroes are the Force Commander, Apothecary, and Techmarine. These heroes specialties play off each other really well. The Force Commander is a melee specialist who charge into superior numbers of enemies, the Apothecary can support him and surrounding troops by healing, and the Techmarine can build turrets and teleporter relay beacons to keep re-supplying the armies in the forward lines. When the three heroes are working together, they can thrust into combat, keep their backbone strong, and prevent counterattacks.

A side note for those interested (tiki). They have the system requirements posted on the forums of the official dow2 site. They also have a release date for the beta…

“The beta will be hosted via Steam and offered exclusively to Warhammer® 40,000â„¢: Dawn of War – Soulstorm owners on January 21, followed by a worldwide public release on January 28. The beta will feature all four playable races, five multiplayer maps, and Microsoft\’s Games for Windows – LIVE TrueSkill Matchmaking.”