I followed the tutorial guides using MBED and got the BLE Nano's demo programs working within about half an hour. One reason I gave this product 4 stars is that the instructions for loading the firmware onto the DAPLink (USB programmer) were not very clear and I'm still not sure if I did it correctly. Another reason for 4 stars is that MBED (the online IDE you can use) was often sluggish or unresponsive in my browser. I'm considering using one of the alternative IDEs. Programming the BLE Nano was very easy. Just drag and drop the generated hex files into the DAPLink and it immediately starts working.
Aside from those quirks, I was able to establish communication with my Raspberry Pi using Bluez and BluePy. When attempting to pair, be aware that this BLE module does not use the default public addressing for communication; it uses random addressing. Also be aware that BLE is Bluetooth 4.0, which is not meant to be compatible with earlier bluetooth versions.
EDIT: If you get tired of using the mbed IDE like me, I recommend using the Arduino plugin. Don't follow the dated instructions for setting up the arduino/GCC environments on RedBearLab's product page because they no longer work. Follow the instructions on their github page for the arduino addon (linked in getting started guide) I couldn't get anywhere with the GCC tutorial because I could not find the older version of the SDK they used.

I always buy my fun electronics from Sparkfun. I used them for years, never had a problem!

nice BLE module, especially for Arduino, simple, reliable and tiny.

In less than an hour after opening the box, I programmed the BLE Nano using the Android IDE, and had the BLE successfully appear as a BLE Beacon detected by my Android phone. I love the number of detailed example Sketches, one of which is a BLE beacon.

A couple wishes: 1) long pin headers on the dev board so I can plug the Nano into the dev board and the dev board into a breadboard: as things are, I'll probably plug the dev board upside-down on a breadboard via long headers, and run wires to the Nano, plugged into the same breadboard). 2) Update the Arduino plugin installation instructions to match the github instructions, 3) add more complete instructions around installing the serial driver on Windows 10: I had to try a few times to get around the "I don't see a board" installer error and mysterious "error occurred" messages, 4) Mention that the board needs a USB extension cable (e.g., CAB-00517) rather than a mini or micro USB cable - luckily I had one lying around from programming my MicroView.

All in all, it looks perfect for all the BLE work I want to do, and I love how tiny it is!