Its a pretty average shurflo kit. Most folks who build their own, can piece together the same setup for about $100-$150 less, depending on what you need for your application. If you don't want to go to the trouble of finding and ordering all the pieces it would be a decent starter system. If your spending that sort of money you ought to also look at the SMC water injection kit before you make your choice.
The advantage of building your own is you can get just the pieces you want instead of using a setup that is pretty generic. I've actually spent a bit more on my system but I built it up a few pieces at a time, and I built it just the way I wanted it. The learning process as you build and refine the setup is also very valuable.
The Aquamist is the top of the line, but will set you back a bit more money.
Almost any water injection setup is a good deal when you consider the value for expense.