The AKAI Professional MPK Mini is lightweight without feeling flimsy (except for the miniature piano keys themselves). The rubber feet keep it quite stable on a stand next to my workstation. It has no power input (or audio output) besides the USB bus, so, while eminently suited for use with a laptop (or other workstation), is not useful as a controller for a tablet-based synthesizer. Nor do the small keys lend themselves to on-stage playing, at least for those whose hands are accustomed to standard piano keys. I found these two points disappointing, given how obviously portable the device is.
As a desktop controller, however, it shines. With the option to use keys or (velocity and pressure sensitive) pads for input, it works well with the (free download) MPC Beats (and was immediately recognized by Apple's Garage Band). This beginner was quickly able, after watching a fifteen minute YouTube video, to record a basic sequence beat with a bass line and play a synth lead atop, with little more effort than would be required for a solo artist with a looping pedal. The joystick combines pitch bend and expression sensibly, replacing two separate wheel controllers, and the parameter control pots feel very sturdy.
My largest complaint is with the non-intuitive and rather cumbersome licensing of the sound libraries. On my Mac, the included libraries downloaded and appeared to be applications, but would not launch; a third-party licensing app required creating yet another online account, and I'm not entirely sure it unlocked all the libraries. I would have appreciated an obvious step-by-step guide rather than hunting through online FAQs.