I know for a fact that Cubase 7 (7.0.7) is stable, and posts to the contrary are purely the result of user error.
Well isn't that an interestingly bold statement. I have renewed trust in c7 and now it is time to buy.
I used to upgrade every year to a new system. Then it moved to every couple years to today where I don't remember when I built my system. People get to the point where cutting edge is not necessary and will stick with what works. Most studios I worked in when i was younger were that way. Once your rig was refined and stable, everything stayed put for a looooong time.
That is where I am now. Everything I need works really well so I stick with it. I don't need more. Why change anything?