1. It's pretty straightforward as a MIDI sound source for a DAW/Sequencer. 16 channels in and out. It probably helps to have a Performance called up, as this makes easier the 5 MFX insert effects routing (there's probably some sys-ex you can use to externally change the routing, but this seems a lot easier!), plus you can Link it to a particular MIDI Setup, so you can determine in/out channel reception, etc..

On the whole, no problems.

I still recommend doing your initial style rough 'capture' using the internal Sequencer though, then saving and transferring the SMF to your DAW for fine tuning there. I still think the accuracy of the capture is better inside the box rather than over USB or MIDI. This was how it was with the G70, and honestly, most things I've tried.

2. Yes, that seems a doable scenario. I'd shoot for .WAV's or .AIFF's rather than MP3's, because they push the processor less hard if you tempo or pitch change the loop. Overall, for the best sync, I wouldn't want to move the audio away from it's original pitch and tempo, if you want to do loops that are really long. Plus, they sound better than MP3's and today's USB sticks are large enough to be able to use full bandwidth audio without filling up too soon..

3. The lever has NEVER been straight on/off. It has always been capable of being shaded. The problem some have with it is it can be quite short throw, so you have to practice not simply yanking it up fully if you don't want maximum modulation. If you ever played something that felt on/off, it was probably faulty.

4. No, unfortunately, there's no access to the internal ROM styles' folder, like you could with the E/G series. Maybe at some time in the future, a user much smarter than me could hack the ROMbin file that loads them all up, but this is beyond my abilities! However, even on the E/G series, you could only replace a ROM style with one named IDENTICALLY to the ROM one, so it really was only of use in storing your style 'tweaks', not in replacing one style with another totally different one (unless you named it after the old style). It was a DB thing...
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An arranger is just a tool. What matters is what you build with it..!