1. The most un-intuitive synth I ever had the misfortune to play without having some kind of manual. There is a manual but it really is basic. This is not Behringer's doing, obviously it's how the ARP was designed. First got it out of the box and TBH didn't have a f**king scooby how to get it to play.
I think it took me an hour and a half to get it playing on a keyboard or via midi. It was reasonably obvious how to get the CVs to be controlled by keyboard, but for at least an hour it gave me a constant trigger - weird.
Finally figured out I had the mixer outputs both up - there's one for VCF and VCA - and if you have the VCF up, it gives a constant note (even if you have the ADSR on the filter with no release - it still sounds constantly) - I just don't get why it does that? Possibly some modular people can enlighten me?
So, anyway - took a lot of self restraint not to twat the bloody thing with something heavy.
And points to Sweetwater - found an online eejit guide to basic set up - very useful. It sort of made sense once I'd set up a basic patch, but it still is one weird synth. Some of the sliders - not sure if they even relate to the patch points and the labels under them.
2. Envelopes - not its greatest feature. With attack on 0 it clicks quite a lot. Might be able to sort that out with other settings, but not great. So to stop the clicking even a little attack is pretty slow compared to most other synths. Haven't tried it out yet, but I'd imagine not good for percussion. Maybe the ADSR is better than the AR filter - dunno yet. But having been caught out with the non-stop trigger with VCF audio output controlled by ADSR - not sure the ADSR will work for VCA properly.
3. Filter. It's an odd one but I like it. Initially sounded a bit vanilla. TBH I'm not sure I figured out its character yet. It seems to have a very small range at any kind of resonance, but once you figure out to sweep the osc frequencies, the filter picks up again, and it often sounded quite different at higher and lower frequencies. There were some occasions it sounded like a different filter when you play mids and basses. And it self-oscillates beyond useful, so it has grunt for sure.
4. Filter types. Not sure I could hear any difference at all. I need to play a lot more to be sure - but initially - nada.
5. Oscillators. Well, as I mentioned, it's a f**king fruitcake to program. I still haven't figured out how to even choose between the different waveforms - it seems like you have to patch just to dial them up - thought it was supposed to be semi-modular? On almost every other synth I ever had, you just dialled up either with knob or slider - a simple choice of sine, saw, pulse, PWM etc. The sliders all seem to be for frequency control, not wave choice. Bizarre. Some old synths were quirky, e.g. Korgs call their filters differently to everyone else, but my first MS10 and MS20 didn't take long to figure out at all. I'm sure I will figure it out, but for the life of me I can't find the VCOs. Was looking forward to all kinds of modular routings on PWMs, but I can't even dial up a PWM to start with...I heard it doing some PWM stuff and it sounded great, but no idea how I did it
6. Build quality. Despite the usual Behringer trolls, who seem to have set ideas about Behringer - it feels solid. Better quality than many other synths I've had. Solid metal case, the sliders don't wobble, and they're smooth. Very impressed with how it feels. Built like a tank.
7. Gizmos. It lights up like a christmas tree. So loads of points for that, even though I can't work the f**king thing.
8. Features. Looking closely at it - lots of potential. The ring mod is small but cos of the patching, should be able to do weirdness. Some sections I have no idea about, but they look like real modular CV control for esoteric patching - inverters, multipliers etc.
9. Midi'd it up on some housey kind of bouncy track I have going, just for easy. Prolly not the type of thing a 2600 should be used for and...not that great really. I could use it for acid lines for sure, and all kinds of bleeps and boings, but I think it prolly shines more at weirdness, long developing sounds, sound FX and S&H sequenced kind of stuff. I suspect I'll use it more for when I do dub or ambient rather than more dancey stuff. We shall see.
Anyway - f**king frustrating. Don't regret buying it at all, cos I know it'll get easier, but much more of a bastard to program than I thought it would be.
So 2600 even more. 
Y'know - "this is the plug", "this is a hole you put a cable into - there are many of them", "don't let your kid stick his fingers inside the thing that says high voltage" kind of thing.
