I agree on Kestrel. I've also had one for several years now and it has never failed me. Very well built, accurate and sensitive.
Most values it measures also update pretty much in realtime.
If a handheld sensor is what you are after, a Kestrel is a very good choice.
They also sell an optically coupled serial interface for using a computer to log the unit if needed. I think the serial interface can be used to dump the devices internally stored logs plus it allows for realtime monitoring on a computer.
Key sensors are made to be user replaceable. The wind speed sensor is a small fan looking insert that can be popped out with your fingers and replaced all within seconds. It uses a magnetic or hall effect coupling method so no physical signal connections are needed.
The temp and humidity sensors are also made to be swapped out easily. Kestrel sells a humidity calibration kit with different salts for creating different humidity values in a provided container. Just place the unit in with the salt and calibrate it to the value of the salt you are using.