There seem to be a difference of opinions here. Having had short rides on both the first and current versions I'd say both sides have some merit.
On the plus side the latest G2 I tried did seem quite an improvement on the first version. The motor seemed a lot quieter, more powerful, and the control system much more sophisticated. I was impressed by its performance, the riding position is good and the suspension does take some of the sting out of the small wheels. The disc brakes work well, it's very light for an electric bike and the enclosed chain seems a good idea.
Now the downsides. As has been pointed out it's not compatible with most normal cycle parts or accessories, so you're stuck with Gocycle for these. The luggage carrying provision seem to be an afterthought rather than built into the design. They list a seatpost rack (£100) in their list of accessories but don't seem to feature it in any photos, or show if/how it fits into the carrying case. Likewise the front carrier.
Perhaps most importantly it can't really be described as a folder. Yes it does disassemble into a small package, but nobody is going to want to do this at the beginning or end of every ride, or when getting on or off a train.
At its present price point (£2499.00) it would appear to have a small market. Those who want something a bit different and are prepared to pay for it, those where its light weight and ease of disassembly might be top of the list, such as those living in small inner city flats, and those just attracted by the clean looking design - it would look less out of place in a living room then most bikes. And Smart car owners of course, it might be one of the few electric bikes to actually fit in one.
Overall, for me, its a good attempt at something different – there are far worse examples. If its many good points could be combined with the folding and practicalities of a Brompton I'm sure there would be a winner.