it's one of the least intrusive or annoying drm schemes out there, however I don't buy any games except Valve ones via steam because I like to have boxes/discs and while valve promises to release fixes for their games if they ever close steam, no other companies with games on it promise the same thing.
It's much better than when it was new, it rarely crashes anymore and I doubt it's anymore spyware than other drms. And surely less than WoW's Warden, starforce, or any of the other really nasty ones. There are voluntary stats collection every once in a while about what your PC has, so then Valve publishes the stats for everyone one to see. Basically stuff like the percentages of people with proc speed/cores, gfx card generation/mfg, total ram, total hdd, type of internet, etc.
I'm not a huge fan, but there still isn't too much bad things to say about it, so I'd say try it for Valve games at least and if you like it, try it for the other games they offer too.