This is a very delayed reply to HarbingerOfDeath's comments about Steam:
Some of the concerns of STEAM are:
1. Not having control of what goes on - not seeing exactly what STEAM is doing to your files makes some users uneasy.
a. Being able to patch your game at your own leisure is sometimes necessary if there are side effects of the patch (losing save games for one).
b. Theoretically it may be possible to not only download files, but also upload files.. using your PC and bandwidth as a file server.
d. Performance hit - Is a mid to low end PC going to take a significant performance hit in a single or multiplayer game with STEAM running in the background?
Pretty much EVERY piece of software out there does things without explicitly informing you of what is going on. So, I don't know why Steam has to tell you step by step what it is doing.
a. Steam gives you complete control over what games to patch. Except for patching itself, that is.
b. "Theoretically" ANY program you install on your machine can do this. Next?
c. See b.
d. Not true. I have a friend who plays CS:CZ on a P3600 with 128MB RAM and a GF2MX at 90+ fps. If you know anything about computers(I'm a software developer and hardware architecture designer), then you'll know that every computer is different. Just because a computer has the exact same hardware as another, doesn't mean they'll run the same. Unfortunately, there's too many variables and the biggest is usually software. Drivers, OS, Spyware, AV Scanners, etc. So to say that Steam doesn't play on low to mid end computers is simply a lie by generalizing.
OK. To sum up concern number one, you're afraid Steam may harm your computer. It is a valid concern, but if you trust the developer and publisher (namely, Valve) then it shouldn't be a big deal. I mean, I'm sure you wouldn't worry about installing Photoshop because it MAY have spyware or it MAY use your computer to upload files.
There's no logical valid reason not to trust Valve, so far.
2. Your PC requiring Valve's servers much in the same way a MMOG requires servers could be a problem.
a. Look at WoW and SWG. They had problems recently due to a tornado hitting their server farm. WoW testers were not able to log in this weekend. Imagine not being able to play your favorite single player FPS because of this.
b. Situations where local internet is temporarily not available
c. LAN games - will they happen with HL2?
d. If a million people send an authorization request at the same time (release day.. whenever that is), will STEAM be able to handle it?
a. Without Steam you had WON servers. If they were down, you couldn't play. As long as you want to keep piracy and cheating down, you need central servers. Yes. IF they go down, you can't play. Oh well. EVERY major MP game is like that, today (Tribes 2, COD, BF1942, SOF2, etc.) So, Steam is not unique in this area.
b. So, I had a LAN party at my apartment, one night, and my internet was down. We could still play CS:CZ, locally. You don't need internet access to play SP and LAN games.
c. See b.
d. I don't know. I hope so, but then again, this technology is new and it'll take some time to perfect it.
Steam has all the advantages and disadvantages of any remotely-distributed-centrally-controlled-network client =P. The possibilities of it doing something mean to your computer are as low as any other product from another major publisher. And, simply put: You will have to get used to Steam because this will definitely be the way games will be published more and more.