Have S20 in 308. Only picked up recently Have put about 50 rounds through it. Had a single misfeed (in that the cartridge was not picked up by the bolt) but it was me not cycling the bolt properly.
Issues I've read about are rattly magazines (mine is fine) and misfeeds on the mag (I think there is a fix sold on eBay for a few quid). I knew about these but still went ahead as I liked the fit and idea of the rifle.
At the range it was very accurate.
One thing to note is the style of shooting it fosters- the Thumbhole and the cheek piece, along with the integrated rails which dictate scope placement to a certain extent mean I have quite a head down and forward style of hold with it. This feels quite different to other rifles I have which have much lower open combs (hogback etc). It's definitely a more 'locked in' style of hold. I think that will be conducive to accurate shooting but maybe slightly less versatile than a straight sporting rifle. I actually ended up dropping the comb a little from the setting I had it on and removing some spacers to create a shorter rifle to make it a little more flexible. I'm still playing around with mine but I may need to add a rail so I can bring the scope back and closer to my eye to give a more relaxed position with eye relief.
I think it's an interesting concept, and whilst I'm still playing around, I think once I've worked out what I'm happy with RE fit it's going to be a very good, accurate, solid rifle. That being said, it is something a bit different
Hope that helps, happy to answer any questions