I'm 27 and have been playing games since the 8k Spectrum. I've also owned a Commodore 64, Amigas and many PCs, starting with a 386. Steam has only improved my long-term hobby. In fact, I've even added most of my classic games collection to my Steam list.
I also used to play a lot of CS (pre-source) and having Steam back then would have only improved the experience. Apart from the odd 'Steam is already running' (very rare and easy to fix) I've never had any problems with it. You must just be unlucky.
I am also 27 and have been gaming since the speccy +2 and i must admit when i had to move from the WON network, i wasn't best pleased... steam was buggy and it took an age for them to get friends working correctly. However, steam is now great and i have no issues and if wasnt for the cost would have all my games on that platform.