I've tried a lot of grooveboxes in my time, and the OP-1 is one of the only instruments I've ever seen that has worse value-per-dollar than the DSI Tempest. Very few instruments are expensive and useless enough to justify this; the OP-1 is solidly among them though.

All I'll say is that you should reserve your judgement until you've tried some competing products. The Playmobil laptop looks like a great way to do your Word documents until you try a Dell or Apple machine.

Which one would you recommend? For an easy to use low end starting point.

I'd probably recommend the Model: Samples if you're interested in sampling, or the Novation Circuit if you want to focus on synthesis. The Model: Samples in particular is great - it's an adaptation of Elektron's more expensive Digitakt that puts the core featureset in a more focused box. It would probably be my sub-$400 desert-island groovebox choice.

Edit: it's worth noting that both of these systems are sequencers, not tape recorders. I consider that a benefit (much longer record times) but if you want a multitrack recorder then you should look elsewhere (maybe a 4iXo DAC?)

OP-1 owner eh ?

Sure it's cheap if you compare it to Stradivarius, but if you use instruments in same type ("a CPU feeding ADC/DAC with some knobs and buttons") it is one of most expensive one in category.

OP-1 field (the only version they sell) is 2000 EUR. That's top end of synth world and you usually get more knobs and keys with that. That's the price of Korg/Roland/Yamaha workstation-level keyboards.

Do NOT try to compare it on price with anything, it will always look like a bad joke. Subjective, might be worth to you etc.