There are also quite helpful resources that take a lot of the calculation out of it for you - I was just playing with the Sous Vide Dash app to figure out cooking time for a beef tenderloin and you basically just put in a few measurements like start temp of the meat and size and desired doneness and it gives you all the info you need to set things up, plus lets you see how the process is going with regards to safety. (I want to cook the meat to rare/med-rare but hold it at temp long enough to kill bacteria all the way through, because my mom is immune compromised. The little chart shows me when the exterior is 'safe' and when the interior has gotten to a suitable safety level for the various common pathogens, it's pretty nifty.)
And to be fair, I'm not sure I would have bothered had I not been dealing with immune compromised people where being able to take the guesswork out of if something is cooked long enough is a big bonus.
