So, when a letter comes in the mail to us and the address appears hand written, has a standard stamp as opposed to being metered, comes in a plain envelope or even one which looks like an invitation style envelope and so forth, we are curious.

Absolutely use a stamp over metered and just use any stamp.

Go there after dark and pull the electric meter out (quickly) and take off with it.

Other lists would be much better:Code violationsDead meters

@Dan D.A big factor that I would consider is weather or not the duplex is individually metered. the thing i like about SFR in my town is that all utilities including water, sewer and garbage, are all paid by the tenant.

Are there separate meter for electric, water and gas?

You may have saved yourself some grief, because your "rough area" meter was on high alert.

If you have been lurking that long, then you know I have a great BS Meter, so I just don't go there with some hair brained idea unless I really need to. 

Has anyone noticed any substantial change in response rate when shifting a mailing campaign from 44 cent first class stamps over to the metered option?

Peoples' B.S. meter is pretty sensitive when going through the mail.