So far I have only tried this baby a couple of times, but it is actually surprisingly easy to use (although fairly difficult to clean). So far I have found that the grind needs to be suprisingly fine and that for ideal results - at least with this unit - one will want to use pre-boiled water and also extend the brew time slightly by holding the vessel on the right down (by lifting up the counterweight on the left) for an extra 30 secs or so. This way you will get stronger coffee - both due to the longer brew time, but also due to getting more of the water from the pot on the right to shift to the glass on the right.
The temperatures seem to be good as I have not detected bitterness in the cup, i.e. it appears to cool down sufficiently from the boil while making its way through the siphon tube.
What I have detected is a clear and clean cup of very tasty coffee. Better than I have ever managed with a French Press. And the Balance Brewer certainly looks the part - and I suspect it will be a nice conversation piece over a good after dinner coffee.
Any downsides? It's early days, but I've already mentioned cleaning. It takes a bit of time but is manageable (although I would not use this on a daily basis). The bigger gripe for me is the little faucet used for dispensing the brewed coffee. It is fairly small and it takes a while (too long in my opinion) to serve the coffee. The maximum capacity of this unit is around 400ml and there is a bit less of the finished product. So no this cannot be used to entertain larger groups (although larger units are available).