First off, I don't own a real Juno 6, but I have been the proud owner for over 10 years of a Juno 106, so I'm coming at this from that angle.
When I fired up this plugin and started playing around, I recognized instantly that it did have a certain amount of the character of a Juno, particularly in the filters and the chorus. Great Job!
I didn't care for the oscillators, though, I think they need some work. There is extreme aliasing on the upper register, and the lower register doesn't quite have the pure, raw, slap-across-the-face kind of beefiness I get from the real deal.
The GUI is a real pain, as well. I understand they're trying to go for an authentic look and cop the interface of the Juno, but it's just hard to use. You can barely see where the sliders are! And while the arpeggiator is authentic, I would at least like the option to sync it to tempo. It's a lot harder to find the right tempo adjusting a tiny virtual slider you can't really even see than it is on a real slider you can grab and move. And why bother replicating a feature that was a pain in the first place?
There's a decent selection of presets, many of them remind me of sounds from my Juno 106 (particularly the darker ones, since the filter sounds much better than the oscillators). Some of the presets make no sound, for some reason, usually tweaking up the cutoff fixes that. Not sure what the intention was with those patches, though.
If there's a manual I haven't come across it yet, but who really needs a manual for a Juno? It's all right there in front of you.
I have to give this project props for being open source and free. Free is cool enough, but hopefully the open source nature prompts significant improvement and maybe even some spin-offs. I'll be waiting for the next version before I put it much to use, though...