It is defintetly a convinence, but not required. It can significantly cut install times. Especially helpful for stubborn bolts.
If you plan other DIY adventures I would definately recommend. Air tools can be pretty pricey, but you can get the electric impact cheap (less than $50) which I found helpful for removing lugs. Which if you have the wheels off alot (brake jobs) is very helpful.
I also used this to break loose the top nut on the struts.