digitals fail and always at the worst time. I've had several different ones. The Coralife ones seem to always fail. The Sylvania one that I have has done ok so far. The ones that have set pins works best but even those will eventually fail to keep accurate time.
i have some lowe's timers on my fish only tank. not really a problem with them ever. except they are so big and blocky. and if the power is ever out or it's unplugged, i gotta respin it to get it back to normal. kinda annoying.