I love the op1. For me, its easily the best small synth/instrument of the decade, so my review is probably very biased.One of the best things about it, is the tape recording aspect and its simple workflow. If you don’t like that workflow, then you definitely are cutting out a huge part of the op1.
For you questions:
The first two are completely subjective. imho, its very worth it, and not a toy.
What it does best:
I would say that the 2 biggest strengths of the op1 are:
a) its tape workflow. Simple cut/paste operations and a visual interface that shows you where audio is on what track, make for very effective ‘quick and dirty’ workflow for editing. You can make whole tracks inside the box.
b) it fully supports an unquantised workflow. There are sequencers that play to the beat, but imo, recording unquantised to tape is what sets it apart from groove boxes like the elektrons etc. You can make any loose style of music very easily this way, without shifting trigs, or other post operations.
What it does worst:
I would say its not a good controller. If you want a midi controller, there are better cheaper options. Using the op1 mainly as a controller is (imho) a real waste of the machine. Rather use an iPad where you have many many advanced apps that can do way more in terms of sequencing and pattern recoding etc etc etc.
As far as using with your modular:
I think simply playing along with the modular is its strength, chords and the like. If you want to sync up completely, there are options. USB midi into your modular is possible, as is a click track output from the beta OS.
For sampling and routing… it really depends on your workflow. Yes you can sample in easily and output back into the modular (will probably need something to boost the audio signal). But it doesn’t have a specific internal mixing/sampling workflow like the way you can use the Octatrack to sample while playing other material and flip over with the fader. If you want to do those kinds of things, you will be disappointed in the op1.
I think its been made pretty clear over the years that the op1 has quirks with its workflow and you either LOVE it for those, or you don’t. If you used the op1 before, I think you know in your gut already if you like or dislike the machine. Its still the same machine and the same hiccups and oddities are there.
There are no shortage of videos on youtube, but here is one of mine where you can hear its unquantized and scratchy resampled nature, that I love about the op1. There is a keyboard part recorded in (the same way you could use the modular if you wanted) but the rest is all op1 and the track is heavily edited and resampled all inside the op1.
That’s my 2 cents, lots of people use the machines in different ways, and I am sure there are other perspectives and cool ways of working.