I've been using the midiplus X3 mini and X4 mini for about three years now. You will not find a better MIDI controller for the price. The keyboard is solid, level, and well-built. The keys themselves are satisfying to play, with a nice resistance -- neither too stiff, nor too giving. The keys don't feel quite as nice as the Arturia KeyStep, but then the KeyStep is more expensive and has many features I don't need.For those of you using external hardware synths with 5-pin DIN inputs (i.e. the old-fashioned MIDI ports ubiquitous until about 2009), you'll be relieved to finally find a decent and affordable MIDI controller that can send MIDI to your gear. That's right: this midiplus MIDI controller is useful for DAW-less (i.e. non-computer) workflows. I personally use the midiplus X4 to control an Elektron Digitone and a Roland MC-707, and it excels at this task.These mini midiplus keyboards are a great size and form factor, virtually ideal. The X3 mini fits nicely in the slide-out tray of a corner computer desk, while the X4 mini fits nicely on a 31" folding table on which I like to improvise melodies and chord progressions with external hardware synthesizers.One nice thing about the midiplus mini keyboards is their horizontal span. On normal-sized keyboards, it's a stretch for me to play 10ths, and 11ths are impossible. But on the midiplus mini keyboards, I can easily play 10ths, and 11ths are possible with only slight discomfort. This is a important for me because I'm a composer who often likes to use 9ths, 10ths, and 11ths in my chords and riffs.It's also super convenient to be able to quickly change MIDI channels and velocity settings: the midiplus keyboards allow this, and more. You can also reassign the MIDI CC messages that each knob and button use. For instance, knob 1 uses CC 7 by default, but you can reassign it to any value, such as 92. In practice, this means you can use these 4 knobs to actually control a dozen or more MIDI CC parameters. (But you'll have to change the CC assignment on the fly, which is a somewhat awkward process made easier by repetition and memorization.)I only rarely use the 4 knobs at top to control filter cutoff, resonance, volume, etc, but it is nice to have that ability. Though smallish, these 4 knobs have a really nice feel and resistance, too, with a non-slip coating.The capacitive touchstrips on the far left, for controlling pitch and modulation, are better and more responsive that I'd hoped for. Yes, they're a little bit imprecise and coarse-grained, but they are useful for trying out ideas, and good enough for improvisation.Caveat: I'm not a pianist or even a particularly good keyboard player. I use my midiplus keyboard to compose music and try out various ideas/riffs/phrases/chords. For my purposes, these midiplus controllers are close to ideal.For my uses, there are only two defects with this midiplus keyboard. It lacks an expression pedal input, and it lacks a dedicated power supply (DC-input). So I have to power the keyboard using a USB cable connected to a USB power brick. Kind of annoying, but certainly not a deal breaker.