Steam has their own protections that aren't as invasive as SecuROM.
Picked up the game from a local Circuit City (they've got it on sale), after install and activation (which wasn't a problem) I went to gamecopyworld to get a mini-image.
The security protections make running the game with disk a pain in the rear, and heaven forbid you uninstall and reinstall and SecuROM decides you have installed too many times (as my friend with the gaming rig discovered). Then you have to call the company provide a PICTURE of the CD, the Manual, and the game BOX before they will help you reset it. Just as likely, you will get the runaround through the various departments and never reach someone who can tell you that without a ready digital camera, it will be a week or more before they'll get your pictures. Nasty.
That said, the demo doesn't do justice to the game itself, which is highly story-based and the gameplay drives the plot by allowing you amazing flexibility in playstyle. I'm not a FPS fan in most areas, largely due to the fact that I require a plot more than find key card A and insert in slot B. ^_~ This is the only FPS in a decade that has held my interest. I won't go into the plot due to spoilers, but it's worth picking up.