It sounds like your load was too light? At light loads it will skip some on cycles as needed to maintain voltage regulation, similar to discontinuous mode in other chips. It also could be that you are trying to run it too fast, if Tc is too small you will get multiple osc cycles for the inductor tuned freq.
Ideally the on cycle is delayed by the comparator until Vout drops below Vref, then it will turn on only for the reaminder (less than 1 on cycle), and be turned off by the oscillator. When it turns off your inductor current will start decaying, so combined with appropriate load, shortly after turnoff the output voltage should be dropping. So for any decent load it should oscillate somewhere around the natural inductor properties, provided you don't have a value of Tc that is way out of whack.
Try using a larger TC value, so for your given load it should be running at every osc cycle or skipping every second osc cycle or so.
These are a great little chip for simple apps, either using the internal switch or just tacking on a PNP on to get a couple of amps output. If you really want something more sophisticated this tiny cheap little chip might be the wrong choice.
You can reduce V ripple a lot, at the cost of a little V regulation by taking the voltage sense from the first cap in your output PI filter instead of the final output. You can increase the duty cycle a little from the typical 80% max, by putting a resistor in parallel with Tc, as Tc is charged at 35uA and discharged at 220uA the resistor slows charging and hastens discharging.