I have used RedOrchestra for years and recently bought Empire: Total War, which is based on STEAM, too.
STEAM is basically a gamebrowser that allows you to buy and download games that are then bound to your login.
This has pros and cons of course:
On the Pro side:
Most games are cheaper with digital download (atm you can buy UT3 for 12USD compared tp 25-35USD normal price range)
The game is automatically updated
The game is bound to your login, not to your PC. You won't lose activations or something when changing computers
You will have easy access, repair and installation-options for games, addon and mods.
STEAM supports Cheat-Protection and offers own technology to verify protected game-content is unmodified, before entering protected servers.
On the downside:
You cannot resell games. This is basically the same idea used in modern DRMs with limited installations. With the limited activations, though, switching PCs without deactivating successfully or when you have no time or no knowledge to backup your activation-registration, you loose an activation. With STEAM, this is not a problem (you can even install it on different systems, but of course only login from your account with 1 PC)
The smart user also realizes another thing: Make several accounts, and then you can also resell games, by selling the account of the game with it.
The most commonly repeated downside is the collected of statistics. STEAM registers how long you play a game and collects this time, to make up an overall ranking for the games and to advertise them to users with similar games installed.
To end another myth: You don't need to be online to play STEAM-games. You can switch the browser to offline-mode and then STEAM also won't send the statistical data online. So, if people complain about the above, it's mostly because they don't know what is going on on one hand and does not know how to end it on the other.
About StarForce:
It's no longer the bad thingy that installs malware on your PC. It's only used for online-activation, now, and doesn't install anything. But SF now commonly used to enforce the limited number of activations. (e.g. with DCS: BlackShark)