Having software on steam will be really cool since updating will be seamless and we can get stuff for really good deals during sales. I have lots of software, and manually updating them can be a bit annoying at times.
On a side note it would be funny if they added this to Steam: http://www.stardock.com/products/start8/
I hope they revamp the UI, since I really don't care for how it's set up, nor do I like (or don't know how to access) my software keys in the event I want to view them (so I know what games are associated with different family members accts).