What I don't like about Steam is that it makes my games take much longer to load (especially if I have no or slow Internet connectivity), and it leaves itself running when the game is done. I also don't like the in-game pop-ups it does.
What I do like about Steam is it makes purchasing games, and managing installs and save games across two computers, easier. The Workshop is a nice feature, as well. It also highlights many indie games I otherwise wouldn't have known about (like Fallen Enchantress). They could use a better browser, but when I'm shopping I just use a regular web browser.
So, Steam has both good and bad points.
Actually you can goto msconfig under STARTUP and uncheck steam loading upon launch. I turn off everything that always sets itself to launch when I boot my computer as you are right it just bogs down your system while all that crap loads. If you don't know where msconfig is I can walk you through it if you need help.
