How do people use chess software to improve their practical skills? I'm currently using chesstempo to get better at tactics, reading books on strategy, analyzing grandmasters' games, etc. 

My current rating is around 1800 and I am planning to gain 200-300 points within the next couple of years. 

I'm considering investing in a chess software either ChessBase or ChessAssistant and would very much welcome some use cases of how you use them to improve your practical skills?
I know that I, for one, have used them to tell me why a line not mentioned in the books is bad. Most books show you all viable lines of play and maybe a few dubious ones, but a book can't mention all possible variations. More often than not, my opponent will play something very early on in an opening that isn't mentioned in any of the books I have on hand and so I assume it's incorrect play but struggle to know why it's an inaccuracy and how I can punish the inaccuracy. This is where, in the absence of a seasoned pro, a computer can be useful. 

Let me illustrate with an example. I am a Trompowsky player and I learned most of my lines from a book by Peter Wells and a video from Andrew Martin. Together they cover a lot of material and I feel reasonably prepared to play at least passed move 8 or so. In many blitz games, however, I was frequently encountering the line:


  
  d4, Nf6 
  Bg5, Ne4 
  Bf4, g5?!
  


Now this g5 move is not listed in any material I've come across. I can probably assume it's bad or it would be mentioned as a viable line, but I couldn't come up with why it was bad over the board. Maybe with careful analysis, I could, but if you are like me, time is in short supply. I am a husband and father to 4 so I need to make good use of my time. Or, in this case, good use of the computer's time. Finally getting tired of seeing this line in view of 


  
  Be5, f6
  Bg3, h5
  


and I'm not sure where the bishop is going to go after h4. So I put the position into the computer after 4. Be5, f6 and let it run for awhile. After some time it came up with the surprising


  
  e3!, ...
  


threatening Qh5#. I had completely missed this and always assumed that the bishop must keep on moving or retreat all the way back to c1 after 3. ..., g5. You can argue that I should have been able to find this without a computer, but the fact remains that I didn't and there are plenty of situations out there where my opponent may play something dubious but I may struggle to find out why it's dubious and what the correct response is.

In sum, I think you'll find it useful to use a computer to refute variations that appear strong on the surface, but aren't mentioned in your reading material so it's not likely that they are as strong as you fear. Computers can easily find those counterintuitive moves that will shock your opponent who isn't as prepared.