I have the Jebao doser. No problems here. You'll need a 100 ml graduated cylinder to calibrate it, but other than that, very easy to use.
Dosing pumps are fairly simple. If they fail, it's more likely to just break and not dose rather than turn on and dose everything. Most of the failures I've seen with dosing pumps, whether expensive or cheap, are due to errors in programming that end users blame on the dosers. If you calibrate the pumps, verify the dosing schedule with RO/DI first, and don't use exceptionally large dosing reservoirs, you should be fine.
Personally, I would do this regardless of whether I use a cheap dosing pump or an expensive one.