This is something that I talked about with Josh, and yes that was an Aromed on his desk in the picture.
Beyond the use of a halogen bulb the designs are radically different. The Aromed has no thermal mass, uses a 50W bulb, and its temperature sensor is behind its bulb. The Herbalizer has an optimized amount of thermal mass, a 300W bulb, and has multiple temperature sensors with one being in the airstream right underneath the bowl.
Both can be set in increments of 1F or 1C. However, since the Aromed's temp sensor is behind its bulb and not in the airstream, the setpoint is only a rough estimation. Because it has no thermal mass and uses a low power bulb, it also can't maintain a stable temperature when being used to the level that the Herbalizer can.
We didn't use the Aromed while I was there, but I have used one in the past. From what I remember it took quite a bit longer to heat up initially, and would produce thin vapor if hit hard. The Herbalizer is claimed to maintain temperature within 5F while in use and I believe it. Based on the stuff mentioned above I'd guess with the Aromed it'd be more like 75F.
Numbers aside, I've hit both and wouldn't put them in the same league. Maybe some of the Aromed owners here can comment on some of the above.
First, let me state that I like the Herbalizer, and can't wait for it to come out.
As far as the differences between the Aromed, and the herbalizer, from what I can tell by the information I have seen so far, is that the Aromed is more "homebuilt", meaning it is made in a way that, there is a chance that less things can go wrong, and built to last. If you need to change the heater, you can go to the store, and get the halogen bulb. The herbalizer uses more harder to get tools, so if things go wrong with the heater, you need them to change things.
The Aromed may have the thermocouple above the bulb, but the way they accomplish keeping the temperature accurate, is by having the hot air accumulate in the screwcap, then having it shoot out into the herb. This is why it has the holes instead of one big one. They also made the aromed to deal a certain amount of air to heat up (3 liters every 5 seconds) so it can heat up to the temperature you dialed in. The way air operates, it rises when it gets hot, so by having the sensor above the bulb, you can measure the incoming air's temperature, and the bulb adjusts to make sure the hot air it makes, is what you dialed in. This is why you don't have to worry about heat effecting your herb when you aren't inhaling, because the Aromed lightbulb dims down when you aren't inhaling allowing the excess heat to rise away from your herb, and keep it cool. As long as you inhale at the speed it is allowed to measure, you will get a precise temperature. This ingenious way of thinking to make a vaporizer, is why you only need 65 watts to make it work, as opposed to 300w that the Herbalizer needs.
The Herbalizer, is perfect for when someone wants to inhale like a bong user, while still getting precise temperature. Now, they will be diluting the vapor with tons of air, but it's still good to have that choice for certain people. The look is also much nicer for those that need the eye candy. And it doesn't use glass so there is less chance to break anything.