I vaguely recall Half-Life 2's launch being pretty problematic.

I started using Steam in 2007 and it was fine. In 2006 there was still some residual animosity towards it but I think the tide had well and truly turned since the early days (and I think there were a handful of third party games on it by then too which I guess was something of a vote of confidence - a few were Source engine titles so they may have got a discount or kick-back from Valve, but not all were).