I'm using the controller as my main composing tool together with Cubase and Garage Band. I purchased the smaller one (M32 version) because it has a smaller form factor, perfectly fitting on my desk, but still has a decent amount of keys. (A bit more than two octaves)
I was surprised how good you can play on the small keys, it's nearly perfect for me, since my fingers aren't that long.
The build quality is rather decent and the keyboard feels good and sturdy. Unfortunately my unit doesn't sit level on the desk, meaning it slightly wiggles a bit. It doesn't disrupt the feel while playing it so it's fine.
You also get quite an amount of software with the keyboard. I'd used the Komplete Kontrol software already, since I'd purchased two plugins from Native Instruments in the past and I really like their products since they are programmed with the user in mind and can be used quite intuitively.
The free sounds and instruments that come with it are also quite decent if you just want to start making music. Keep in mind, that the shipped sounds are more fitting for musicians in the electro/synth genres. You even get a light version of Maschine 2. I didn't test it though.
Since I'm composing orchestral music, I didn't use many of the shipped plugins but rather the plugins I'd purchase in some of their sale offers. It's really easy to install everything, and as soon as you load Komplete Kontrol into a track, you're good to go. I highly recommend to read the quick start guide found on the Native Instruments Homepage as well as to watch some videos on Youtube, since you can work with it quite faster if you know some tricks. Even if it's quite intuitive to use most of the time, there are some functions and workflows you can't find out by trial and error.
To use many of the features like scale, arp and parameter mapping, you need to use their plugin Komplete Kontrol. But this plugin allows you to include other plugins not officially supported by NKS (I guess every VST plugin) but it's not as straight forward as the supported plugins.
All in all its a good keyboard, especially for beginners. It has nice features compared to its price, but you have to consider, that its meant as a hardware product to be used with Native Instruments software.
