This Inquirer article says many people are having problems connecting to the Steam servers to play Half-Life 2. People say that you could always use offline mode to play without an Internet connection, but these people seem oblivious to reports online that many people are unable to get this mode to function properly.
More interesting, perhaps, are the legal agreements that surround a purchase of Half-Life 2. One is that no mention of Steam is on the HL2 box or in the End User License Agreement (EULA), yet it is required to play. The second is that where a gamer buys a copy of the game for which the CDKey has already been hacked, he/she will have to wait up to two weeks to get a replacement from Sierra/Vivendi, since shops will generally not take back opened software. The third is that no copy of the game can be sold without paying Valve a $10 fee to transfer the CD-Key to another Steam account.
The German Consumer Association has recently found that the packaging on Half-Life 2 is misleading.