Have you been buying a bunch of old games lately? Because if so, welcome to PC gaming. Troubleshooting is one of the more basic yet frustrating parts of playing PC games. It's also one of the most rewarding; you get a real sense of accomplishment when you finally solve whatever tech issue has been screwing you up, especially if you learn something new in the process. Heck, I'm setting up a Windows 95 virtual machine right now, because I have a bunch of old 16 bit windows games that I'd like to be able to play again -- and I can do it. Virtual box actually has full Direct X support, so it's fixed the last hurdle that was keeping me from being able to play literally any old PC game I'm likely to come across.[footnote]not to mention already own; a good chunk of my library has been off limits for a couple of years, just like it was in the interim between Windows 2000 being released and VDM Sound (and later, DosBox) coming out.[/footnote]
Anyway, as for why Steam is both awesome and horrible: It's awesome because the sales are so good. It's horrible because those sales come with one of, if not /the/ most intrusive form of DRM on the market -- yes, I'm including Ubisoft's always online BS in that. You see, steam checks the network every time you start a game too, and heaven help you if you have internet when you shut down your computer, but you don't when you start it back up[footnote]a common affliction with laptops, especially if you frequently go somewhere that has internet but blocks Steam with its firewall[/footnote]. Offline mode only works if you either set it to offline mode before going offline, or lose internet after having already started steam and letting it validate itself. Otherwise, you get errors telling you you can't play your singleplayer game because you don't have internet access.