I love the new GO Bars.
They are delicious and have a very nice mouth feel. Surprising, actually! They're like mini cakes. I found that the inside of the bar actually felt like it was melting in my mouth before I even started chewing. Not sure if that was great or not, but it was interesting.
As @iBar said above, I do believe GO Bars may be a little too sweet. It's like eating a chocolate bar. My brain thinks it's unhealthy. Like I'm not eating properly. It might be because of the outside layers of chocolate and icing. My kids certainly prefer these bars. 
I like them much better than Wunderbars, mostly because Wunderbars were too dense/hard and got stuck in my teeth.
I'm not sure if I like GO Bars better than Twenny Bars. They're just different. Eating a few Twenny Bars does not make me feel as guilty as eating a few Go Bars, because of the aforementioned sweetness and candy feeling.
I'm looking forward to ordering more GO Bars (and for new flavors to become available!)