I've had my Sonic Alert, Sonic Boom for almost 18years now - and haven't had any problems with it at all and use it daily.
Most of the Sonic Boom's have a 5 year warranty, so if anything goes wrong you just send it to them and they repair/replace it for free!
I have a house full of Sonic Alert items, and the only thing I've had issues with was a contact on a room signaller - which was repaired via Sonic Alert quickly and painlessly 
It's recommended that all signallers are connected via a surge protection powerbar/outlet. This not only prevents power surge issues, but also "noise" that can cause the signallers to "mis-alert" (espeically in apartments/condos etc with multiple tenants, even if the electric is isolated for billing purposes etc)
If you're having problems with your Sonic Boom, I'd suggest emailing them directly and seeing if they might be able to repair the alarm clock for you.
If you're looking for a very good, workhorse clock I'd recommend the Sonic Alert SB1000 or SB1000ss
