I already had various different sensors before which had self-heating issues (up to +2°C to high), 'bad' accuracy (+/-0.5°C and lots of % humidity deviation), and all deviated to each other. This sensor finally has a very good accuracy for temperature and humidity (if i trust the data sheet). The sensor produces very stable values and doesn't fluctuate. It reacts fast to any changes (e.g. if i open the window). I have no calibrated measuring instruments, but compared to a 'good' thermometer/hygrometer this sensor shows (almost) identical values. The available library makes it very easy to use the sensor.

Delivery was in time and the sensors (at least the first two) are working as expected. Blablabla (to fill to 100 char.....)

I chose this sensor+breakout-board, because I wanted to buy a "state of the art" device, and I didn't mind to spend a few bucks for it (stress:a FEW, not a few hundred). The availability of the filter cap, which is sold as an extra, was also very important for my decision to buy (read on to find out why).
I have managed to to put it to work this week, connected (~4meters FTP cable) to an Arduino+Ethernet shield, in various test runs (over http and MQTT protocol).
The stability over time of the sensor's output so far is really impressive. If you keep the sensor in a room with stable conditions, then there is practically no jitter and no ups and downs in the output (temp & hum). If you breathe at it, you can almost watch your breath passing by the sensor in the output!
Furthermore, after I had managed to make it work in the software, there was not a single error in the output for hours.
So far so good!
After I have finished setting up the rest of the hardware and software(which will take me quite some more time) I am going to test the sensor in its intended position, where the environment is rather unfriendly! That is the reason why I chose it in the first place, because according to the sensor's datasheet it is specified to work with fairly high accuracy in these conditions as well.
I am very curious how this will work out, and I am planning to update my feedback, after I have finished.
I must mention that it took me quite a few trials and errors and some fiddling to make the provided library work. This is most likely because of my programming skills (just above "copy-paste-and-pray-it-works" level). After i have finished programming and error checking,
I will probably contact support on this, I just want to be sure first, that I have done everything I could on my behalf.
I can definitely say that for residential conditions this breakout board is very well worth its money!
Thank you very much ClosedCube and Tindie for making this "high-class" sensor (+accessories) available to us amateurs!

Now this really is a nice sensor, I have found it to be very accurate and fast !, I have compared this to many other sensors and find this one to be the best !, I particularly love the Permeable cap option which I bought to be able to use this in a protected but outdoor environment , Only sensor I have found with this option.
I highly recommend this sensor, and plan to purchase more !