I flew the Sonic 11m in about 20knots for about 90mins in North Wales. Matt from Airjam brought it up to demo.
I thought it was great. After 20mins I was used to it and could do all the stuff I can do on regular LEIs plus of course, depower it totally.
I think the best thing to do if you're going with these style of kites (Sonic, X-Bow or Nova) is forget about the stopper and learn to adapt. To get the most out of these kites, you need to be able to sheet right out. Having no stopper is only really an issue when unspinning the bar, but with a bit of practice you can chuck it and catch it again which feels quite satisfying! The bar pressure on the Sonic was spot on and it doesn't tire your arms out having to hold the bar like it can do on the X-Bow.
I liked the simplicity of the Sonic Bar but there is a trapping point between the cam cleat and the bar and I thought the QR was too easily triggered by accident. Also the bar was a bit fat for my liking but all this is just my preferences, not necessarily criticism.
Having the cam cleat at the chicken loop was so much neater than the Nova solution of 2 PU tubes but was slightly harder to adjust (2handed operation?) not hard to deal with though and due to the huge depower you don't need to adjust it more than once a session unless you want to sheet it in to do unhooked stuff and out again for some bigger airs.
Personally, I'm gonna wait until Flexi release a kite like this because by then the bars will be sorted (oh, and I ride Flexifoil Strikes for Turbulence and they don't sell GK!)
So if that's not an unbiased review, I don't know what is
Oh, and there are rumours that looping this style of kite is for pussies... well it is if you loop it with the bar right out, but try looping with the bar sheeted right in and you'll find they kick your arse like any other LEI!