I dosed manually for about 6 years, so I know it can be done...but I also know that eventually it won't get done due to life. Sometimes you can get around that (for about 6 years :D), but eventually - in days, months or years - the truth of the matter comes around and dosing get missed or screwed up.
Not that a doser is perfect, but it's theoretical more-perfect than me in programmability. :)
Jebao's equipment is scary-cheap, but I have to agree. I've got a DP-3 and it seems to work without issue. The interface didn't wow me, but it does get the job done, so no complaints.
The motors and pump heads seem standard, so if they break or wear out, replacement shouldn't be too bad. (three pumps * $20 = $60 though...almost-disposable...in the finest of our Chinese manufacturing tradition.)