Physically, the machine itself is very stable, and wheel slippage, with an appropriate tyre is not an issue at all. We do some very steep climbs, and I am constantly out of the saddle for them and experience no slippage at all.
Customer services from Bkool is lacklustre to say the least, although they usually get round to your issue eventually, should you experience one.
For the money, it's a great piece of kit, if you have more to spend, you can get better.
That is my personal analysis, but hopefully you will get a wider range of opinion on here too.