Cons? Monitoring the tank for 24 hrs to ensure 90,840 drops of water go in!
I have been doing this on my 2 largest tanks for 8 months now.
You have to check your addition valve daily for flow consistency.
I was using the brass needle valves, like you use on a swamp cooler initially,
but after about 2 weeks, they were unusable! Can't shut them off, or adjust the flow down enough!
Got some plastic 1/4" valves from Lowes, that are working out well.
The other issue I had (with the brass valves) was flow would get excessive, if I wasn't watching it.
I had die off of Apple Snails because of it. I believe they are more susceptible to Chlorine?
Fish never appeared to be affected.
My tank maintenance now mostly consists of pruning plants, wiping down the glass weekly, adding ferts,
and swapping out a filter pad in the wet/dry (one minute job),