Does an appliance (cooktop or double oven) in a dwelling require a means of disconnect w/in sight when hardwired?
If so, does the control knob on the unit meets the requierments as a Unit Switch as mentioned in 422.34.

Please correct me if wrong; this is how I understand it.

If the unit is provided with a cord cap and receptacle, that qualifies as a means of disconnect.
If the unit is hardwired a breaker lock at the panel will meet the means of disconnect

What cooktop, double oven or dishwasher in the market today has a unit switch that shuts off all ungrounded conductors to the unit?

You don't say how many VA.

It can be cord and plug connected provided that the ampacity of the cord, plug, and receptacle is correct.

The breaker at the panel can serve as the means of disconnect. One can install a breaker lock or lock the door on the panel.

Unit switches can count as the required disconnect. In that case one would not be turning off all ungrounded conductors to the unit. One would have to turn off the breaker at the panel if you wanted to turn off all ungrounded conductors.

Its over 300va; So if hardwired the unit switch can count but breaker at the panel must also be provided with a lock?

I personally do not accept / approve operational control switches as the means of disconnect. If there is any substantial energized wiring within the appliance on the line side of the switch, then it isn't a disconnect means.

A circuit breaker located in an air handler where the circuit conductors terminate directly at the breaker would, in my mind, could qualify as a unit switch and therefore acceptable as the means of disconnect.

I recently heard a rumor that the next edition of the Canadian Electrical Code is going to remove every requirement for disconnecting means as long as the main service disconenct is readily accessible and this would be proposed for the 2014 NEC as well.

Nick from your post; you would allow the control on the unit without the breaker lock? Ex. Kitchen not within sight of panelboard?