The HM TDS-3 came and seems to be a nice enough product for home use. The readings take seconds to stabilize:
Distilled water = 1 ppm TDS reading
RO water from grocery store left over from last brew = 22 ppm TDS reading
Unsoftened tap water = 401 ppm TDS reading (478 ppm TDS on Ward report 6+ months ago).
It'll be interesting to see how the unit lasts and the calibration by checking with distilled water. There's a recessed trim pot on the back to calibrate the meter to any known concentration of NaCl TDS calibration solution.