I've used multiple different feeders over the course of my reefing career.
If budget is a concern (and it always is), the Eheim mentioned above is definitely the best in that price level. It's reliable, it's simple, it's programmable and adjustable. It has its limits, but if you're feeding flakes or (especially) pellets it'll do the job and do it well.
If you have the budget to buy the best of the best, the Avast Plank is unmatched. The feeding/mixing tube regulates the actual release of your food into the aquarium, and it prevents a good chunk of the dispensed food from just going straight down the overflow. Additionally, since it allows the food to soak before being dispensed, it allows you to use freeze-dried food instead of limiting yourself to flakes and pellets.
The biggest drawback of the Plank, in addition to its cost, is the fact that you must have some external method - whether that be a timed outlet or an Apex or something similar - in order to control your feedings. The upside there is that your feeding schedule and length is customizable, but there's still some irritation in needing something external to control it.
I do not recommend Neptune's autofeeder. It's supposedly fine, but the one I got never worked properly and certainly didn't justify the price. In my experience, it exists to prove that Neptune could make a feeder, but it also proved that they shouldn't. Noisy, overcomplicated and unreliable, all to give you something that can be equaled with the much-cheaper Eheim feeder.
