Just to offer a non expert view. The picture i seemed to pick up on meters while digging lately is that it's a horses for courses deal. There doesn't seem to be any single stand out unit, although there are several makes like Wagner, Lignomat and Electrophysics that seem very well regarded in the US trade and timber industry.
It's pretty clear these are all solid units, what's not so easy to figure is how good or bad (or indeed consistent) the cheap Eastern sourced units may be.
Woodweb (which has lots of members professionally into milling, kiln drying and wood processing)
http://www.woodweb.com/ is the best source of expert technical articles and user feedback i too found on the web.
The no-pin variety seem to work well when you need to scan large lengths more quickly, but are fussier about surfaces and contamination. There's a view about that says that if you want to cover all the bases you need to buy one of both types.
After that it seems to be a lot about likely build quality, robustness, reliability and required features e.g. species compensation, temperature compensation, LED light VS digital vs analogue scale - most seem to read pretty accurately in a given set of conditions - even the very cheap ones.
Many moisture meters are sold for stuff like house surveys on concrete and so on, it seems to be important to carefully read the specification of whatever you are propsoing to buy and compare it to your exact needs.
Something to watch seems to be the max moisture content read by the meter - the cheaper ones seem only to go to 20 or 30% which is fine for dried timber, but if you are kiln drying it seems you may need one going up to 60% to track what's going on.
It's probably worth paying a bit more for a meter that will cover future needs too. e.g. i'm thinking of getting into a bit of timber milling and kiln drying.
The Lignomat meters are very well regarded - the MiniLigno DX/C caught my eye as it seems to offer all sorts of add-on accessories like a hammer-in probe and so on - not to mention they offer a deal to buy both types together.
http://www.lignomat.com/MoistureMeter/m ... ni.DXC.htm
I've had problems before with Amazon.com (US) refusing to sell outside of the US due i presume to supplier agreements. Lignomat i think are European, i wonder if they can be bought cheaply on line in Europe??
The models sold by Axminster seem relatively unknown on the US scene, but that's probably not a big deal. That said it struck me as a bit odd that the Protimeter (which is made by GE) does not seem to be much known in the US, because they are certainly nice looking units....
ian