I had a bit of cash, and have been working with a portable setup lately that is mostly Koala Sampler, my phone, a Samson Go mic, and a tiny DAC that is literally a USB-C jack to two 3.5mm audio jacks, one in and one out, and decided I needed some more hands-on sound design power.
In the spirit of maintaining portability, I looked to smaller devices. The problem I find there is that a lot of portable devices look like they're about as much fun to design sound on as a VST or app, so why not just spend a fraction of the cost and do that instead? I did end up working out some of the trouble I had getting Csound for Android working, which is great since there's almost infinite sound design potential there if you don't mind coding (which is how I mostly made music for the first 15-years I was doing it.)
I made a track with Csound and Koala, and decided I still wanted something more immediate than code. So, I bought a Microfreak.
I'm sure the copious firmware updates in the 4 years since it came out have something to do with it being way more capable than I had initially assumed (and at the time I was comparing it with Hydrasynth, which is significantly more capable.) It's got something like 24 different oscillator types now which cover a lot of ground from VA, to wavetable, to granular, and even samples now. They're all a bit limited since there are only 3-4 parameters per oscillator that can be tweaked, but Arturia (and presumably Mutable before them) made sure that those parameters are the ones you really want to control.
I've made more patches on it in a couple of weeks than I have on the Hydrasynth in a couple of years. (Mind you, I've made many more finished tracks with the Hydrasynth so far, so we'll see in the end.) It's super easy to dial in usable and interesting sounds. And yeah, you can "freak" out and make it sound like a university student first discovering LFOs, but I find that side of it decidedly less interesting. If I want cutting edge modulation experimentation, I'll code something up in Csound. The Microfreak just effortlessly does great leads, basses, and pads.
Like everyone else who has one complains: it'd be nice to have some onboard effects since it sounds pretty dry without them. Luckily Koala has quite a few decent effects these days. Really, the amount of sound design, and track creation potential between a $350 synth, a $15 app, and an $8 interface is making me feel a bit dumb over the desk packed with hardware I have at home. (Never mind the $1200 phone I suppose...)