Suitability for using a standard light switch to connect to a micro-controller port
In general, yes, you can use these on microcontroller circuits. 

You are correct that contact resistance could be a problem. With mains voltage any layer of grime on the contacts will be broken down by the high electric field due to the high voltage. On a 3.3 V or 5 V circuit you may experience some problems such as contact bounce. 

I wouldn't anticipate any trouble with switches that hadn't been used much on mains for any significant service.