We used Harmon Vinduer a few years ago, and we have been impressed by the windows (with one reservation about the manufacturer's claims regarding the window finish and its ability to withstand the staining effect of knots in the wood - I mentioned this in a little more detail a few days ago in the
Wooden Windows thread). In our case, they were not the cheapest, but they were far from the most expensive either. One of the things that made us choose Harmon Vinduer was that they were willing to consider requests that other suppliers at the time (including Carlson) immediately dismissed or simply laughed in our face when we asked - this included asking for the U-value of the windows (i.e. their insulation rating), fitting a cat flap in a door or window unit, and fitting double doors which would have required widening an existing opening. I would hope that all suppliers would be more open minded these days though, and less rude at the very least - some were better than others, the worst offenders treated us like we should have been privileged that they even deigned to speak to us in the first place.
Slightly off topic, but referred to in a post above: regarding the environmental impact of wooden windows versus PVC windows, there are strong arguments on both sides. Whilst the production of uPVC seems to be widely agreed as being far from environmentally friendly, the process of felling trees, converting them to window frames, and shipping them to their ultimate destination, also has an environmental impact that needs to be considered. I say this as someone that dislikes uPVC and would never opt for it over wood, but I am conscious of the fact that my wooden windows were shipped from Denmark (from a factory that claims to have adopted environmentally friendly practices, but that is only part of the picture). If you want to hold true to your environmentally conscious principles, you should ideally look for windows made from wood from Irish-grown trees (from ethically managed forests), and fabricated by local joiners using methods which lead to the least pollution (don't process the wood using petrol powered machinery, don't treat the wood using environmentally damaging chemicals, etc.).