I wouldn't use an auto feeder if it didn't have a button that allows you to dispense food on command. Those things can be pretty flaky... you really need to run it through 5-10 cycles before you can be sure it's dispensing even-portioned amounts.
If you're going away for two weeks or less, and you don't have fry, delicate fish or sick fish, don't even bother with a feeder. Fish will be fine for up to (and exceeding) 2 weeks without food. If you must get an auto feeder, the Eheims really are well made.
Good luck,
Jim