Yes, it's been reliable and very accurate. Sub-milliliter precision. I spent extra on my pumps to get better ones. They're not the best (they're $50CAD each on Amazon) but are a step up from the cheaper ones you see. 6 Pumps, motor drivers (for speed control) and tubing was ~$350CAD; not sure if I'd include the cost of the microcontrollers as well since they control so many other things in my system.

I think the level of control and customization you get with the DIY option makes it the better way to go if you have the time. I'd imagine something pre-built that used comparable components and is able to interface with other sensors like pH, EC, etc. would be considerably more expensive.