I suppose they are producing for a niche market and the price is not cheap (in absolute terms) although as Mayner states it's probably good value provided the performance of the product can approximate the running qualities expected of modern models.
I'm a little surprised (and a little concerned having placed my order) to hear that the product ran so badly overall. It would be reasonable to expect that a hand made model would have been checked and tested over some track work that at least the majority of modelers would use and should run well. More importantly, I'm wondering about the responses of the manufacturer in offering 'after sales' support for your product that is essentially defective/not fit for purpose when delivered. I do not possess your modeling skill not do I have the support of a local club, and since the company does not accept electronic forms of payment, redress in a situation such as yours might prove difficult after some real distance buying (I'm in the US).
I had asked OOworks if they could add a little more weight so that it might provide an improved tractive effort on a gradient. Apparently it is difficult to do due to space constraints within, but I guess I can add 10g at least! I had considered ordering the UG class also but I'll hold off for now until I see my own U class running well.
Is the problem that the wheels on the loco or tender are not electrically isolated from each other, hence separate tender and loco pickup for opposite polarities rather than all wheel pickup? A Stay Alive decoder should certainly help