I wouldnt use anything else Steam is brilliant build in friend chat fast downloads, and yeh
its slightly more expensive but look at it this way.
You go out and buy the same game on disc you scratch that disk and thats it game done.
You buy it on steam and you download it as much as you like no matter how many times
you format and you are still at the same place in game as you was 3 months ago.
You can still download an .iso and use the key.
Keep your keys in a document, email or in a folder so you don't lose them.
Services like GOG are DRM-free which means that the only thing you need is the installers.
Steam isn't any safer than Origin, Direct2Drive, Gamersgate, Impulse, or any other large digital download providers for that matter, except for the fact that it has the majority of the market at the moment.
That doesn't mean that some games won't be pulled or never appear on it, so you will be forced to buy them elsewhere, or that the platform will last forever, which is highly unlikely.
And you're wrong about downloading the game as many times as you want to, there are quite a few titles with DRM systems preventing that. Not to mention games that require third party tools, namely Ubi launcher, Games for Windows Live, Origin, etc.