I know the books are still warm from the press but even so I'd change a couple of things in those recommendations
1) You ought to be able to get 0.01 pH accuracy* for a surprisingly low price today. If you can do so.
2) ATC is still on the list not so much because you need ATC as because its presence tells you that the meter is digital (absence of manual calibration potentiometers tells you the same thing.
3) Two point calibration is a must have
4) In order to have 0.01 or 0.02 accuracy the meter will have to have 0.01 resolution so that is a must. This is a property of the meter - not the electrode.
5) I'm replacing the double junction requirement with the broader 'junction design suited for brewing'. Double junctions used to be important in brewing because of the formation of silver/protein complexes in single junction designs. This problem seems to have been solved. I discovered the other day that none of the electrodes I use with success in brewing are actually double junction designs and yet they perform in the brewing environment.
6) Renewable junctions are a plus but they add a lot to the cost of an electrode and don't seem to be as necessary as they used to be. IOW I think there have been some breakthroughs in electrode design and I think they have been in the junctions.
Now I'll add a couple more requirements
7) Stable electrode. This means that readings don't wander all over cock Robin's barn within a few minutes of calibration. This is a major problem with some inexpensive meters.
8) Related to 7) is the ability to tell the meter when to accept a calibration reading. (I've been experimenting with a Hanna pHep that is actually quite stable but it decides when to accept the calibration reading and does so too soon so that the meter is not properly calibrated.
8)Isoelectric pH within 1/2 pH unit of pH 7. This is a 'nice to have' as you can correct readings from meters that have isoelectric pH that doesn't meet this spec. This effectively opens up the range over which ATC works properly.
9) Long electrode life. A good electrode will last for 3 or more years.
Hach has a new low cost meter out. It appears to meet all these requirements (except 7 and, as its new, no hint as to how it might do RE 9). Some performance data is at http://www.homebrewtalk.com/f128/fir...er-apa-443205/
*This means the error contributed by meter and electrode is at the 0.01 pH level demonstrable by calibrating and then reading the calibration buffers over time and temperature. RMSE should not exceed 0.01 pH over a small but finite temperature band. This does not mean absolute accuracy as the buffers themselves introduce error of, typically, a bit less that 0.02 pH.