A very good, though expensive, hot-water delivery device.
Positive Product Points
The water is hot enough to brew properly.
It's fast.
You can control the flow over the grounds for better extraction.
Negative Product Points
The carafe has a wide pour, so you spill filling a thermos or small cup.
Awkward aesthetics (but still, arguably, preferable to the bulbous plastic that sheathes most coffeemakers).
Detailed Commentary
The top-rated CoffeeGeek reviews for this machine are very good and my experience matches theirs. I also recommend the videos and advice on Technivorm at Sweet Maria's. I'll concentrate on what I can add.
An unexpected benefit of the Technivorm is I'm using less grounds and enjoying a wider range of roasts. That is, with other coffee makers I was using more grounds and darker roasts to compensate for the under-extraction caused by lower brewing temperatures.
A design benefit that I had not fully understood before I bought the Technivorm is that its filter basket is completely accessible during brewing, rather than being enclosed by the usual bulbous plastic. You can see what is going on, and you have three controls: you can turn the power on and off, you can open and close the valve at the bottom of the filter, and you can stir. This is explained in loving detail in a video at Sweet Maria's. My standard sequence, when I have a minute, is to run the machine long enough to get 2-3 cups into the filter basket (with its valve closed), then turn the power off, stir, let it steep 30 seconds, then turn the power back on and open the valve at the bottom. I haven't seen another coffeemaker that gives you this kind of control over extraction. (Though if you get distracted by a phone call in the middle of this, you can end up over-extracting.)
I'm using a gold filter. I find the plastic filter holder a little hard to get totally clean between brews.
On the other hand, the fact that I'm basically using this thing as a hot-water delivery device, and standing over it as it brews, raises the question of whether there are better uses for $300. You can get a fast electric kettle for under $75, a good thermal carafe for $50, and filter holders are inexpensive. Plus I'll have to replace the included carafe because it pours badly. The kettle pour-over alternative has fewer parts to keep track of and clean, and clutters your kitchen counter less. In other words, I've paid a lot of money for a little more control (the valve at the bottom of the filter-holder), and a little more convenience and safety 'cause I don't have to pour boiling water out of a kettle. Plus the Technivorm can be used like a normal coffeemaker that you turn on and then come back to ten minutes later.
After three months with this thing, I would not buy any other coffeemaker. But I could also see not buying one at all.
Buying Experience
Good. Roastmasters throws in a few extras to effectively discount the price a little.