Both act on the GABAa receptors, hence the concern as to whether or not to use them simultaneously.
Ambien produces weak anxiolytic and anticonvulsant properties.
Klonopin has anxiolytic and anticonvulsant properties, working at relatively low dosages. (0.5 = 10 mg diazepam)

In the case that both taken at night, before bed, these two shouldn't cause any noticeable negative effect. If one were to take both sometime in the day, the sedative effect could be more.