I have a Milwaukee PH56 and I would not buy another one. The Milwaukee MW102, like Nosy has is a better meter for a couple of reasons. First it has a standard BNC connector for the probe, this allows you to buy any BNC pH probe from other manufacturers. One thing is for certain about pH probes, they will go bad because basically they are an organic voltmeter.
Second reason to but a MW102 is because it comes with a dual junction probe, this makes the probe less prone to failure due to the proteins, sugars, sediment that can plug the junction. The junction is an membrane opening in the probe that "samples" or collects ions from the substance being measured. This membrane is prone to clogging when taking wort samples, so after each use (brew day) it needs to be cleaned, dual junction probes handle this environment better. The best way is with an enzymatic cleaner. The other way is a lot cheaper, but not as good, is to soak the probe in white vinegar for 15 minutes or so and then in a 50/50 mix of household bleach and water for 10-15 minutes. This will prolong the probe life and recondition it if it's slow or won't calibrate. Typical probe life is 6-18 months whether you use it or not. Always store in probe storage solution, never let it dry out.
My PH56 is okay, but it's a single junction probe and I have to buy an exact replacement probe. No dual junction probes are available. Sorry to go on about this, but I recently had some problems with my meter and this is what I learned.
As far as measuring hot wort, I would avoid that completely. It wrecks probes. I always measure at @ 80F and I make the assumption that the pH at 80F is about .2 of a point lower in the mash (I actually tried measuring at 145F and found it to be true). pH drops slightly when the temperature rises, I guess it's a little like a battery, the ions are more readily available as the temps rise.
