After a year of delay, Half Life 2 disappoints half the people who buy it. Main reason: Steam Servers. To protect sales, they force you to register your cd keys in order to play "single player game". However, the servers overload and only few who buy the games can actually play it. So far, there are hundreds of complaints in their forum: http://www.steampowered.com/forums. The most anticpated game will turn out the most frustating game in game history. The game may be great but if you really want to buy it, I suggest you neither wait few more months and see if they fix the problems or wait for ps2 or xbox version.
Conclusion, you can never play HL2 well as long as they use Steam Servers. Only buy ps2 or xbox version. Yet, who knows what will happen to the ps2 and xbox version then?