Having always purchased hard copies of games I am a bit apprehensive about going all digital.My main concern once I have a steam game in my library is there a download limit/number of installation on the game.Is it safe to say that I can dump physical copies for good?
The games you buy are yours forever (or rather a very long time) and can be installed on as many computers as you want (unless the game has a limit on its own, but the same limitation would likely be on the physical edition too).
Dumping physical copies is a decision you must make, but as I stated below, Steam has been around for 13 years already, and they are likely to be around for a very long time. I don't like physical copies as buying, storing, moving and organizing them is hard yet losing them is pretty easy.
Steam is generating billions of dollars every year and is unlikely to go bankrupt, and even if it did, most developers would provide a way to move your games to another platform, like most developers did when Desura went bankrupt.