I'm using the Downloader. I used steam to buy Half Life 2 and this is the same premace. I'm currently DL-ing it and it looks like it will only take about 2 hrs. I can keep it going overnight so I don't need to wait. This way I will be able to play it on midnight of the 18th.
As for the accusations that if your computer crashes you will loose it; not true. It even says right on there that if you loose it you can DL it for free. Additionally for the "logging in every time for use" steam had an auto login when your computer started up and an offline mode to play when the Internet goes down.
Safety of discs? discs break, CD keys get lost. I prefer having a legal account saying that I own Pets than a piece of plastic that is easily scratched to the point that it won't work anymore.