This commentary is based on my own observations and my summary of entries in the CoffeeGeek, alt.coffee and HomeRoast Digest forms. http://themeyers.org/HomeRoast/index.htm
One of the most important determinates in coffee roasting is the use of the second crack as an indicator. The noise level of the i-Roast2 is so deafening that the second crack is almost impossible to hear, (noisier than the original i-Roast). The CG & HRD suggested several ways to remedy this: use plastic tubing at the bowl as a stethoscope, put your ear close to the top vent of the machine, back away from the machine, wrap a towel around the base of the machine, (this worked well for me dampening the noise, so I could hear the cracks). Color and smell are not the best indicators, for a learner, of when to stop the roast. Different i-Roast2 machines with the same beans and the same roasting profiles produce vastly different results, (a first crack on one machine at 5 min and the other machine at 9 min). (Cracks are more audible with some beans than with others). The thermocouple temp curve on one i-Roast2 showed the machine did whatever it wanted to do regardless of the roasting profile. The temperature indicator during the roast is sometimes as much as 30-40 degrees hotter than the thermocouple readings inside the bowl. Roasting batches too close together produces different results, even with the same green coffee and profiles. My machine runs on the hot side, so if I roast for the length of time suggested by many profiles, I get something that looks like it was swept by a forest fire.
Thanks to a 1/9/06 post on the CG Forum, I have a profile that works well for SM Monkey on a hot running i-R2:
4 minutes at 350
6 minutes at 380
3:30 minutes at 430
This variation on a Sweet Maria's profile gave me a good profile for their Classic Italian:
2 minutes at 350
3 minutes at 400
3:30 minutes at 460
My batch size for both is 148 grams.
I use these profiles as a "set it and forget it." I know this flies in the face of conventional wisdom, but it works for me and I don't have to deal with the noise and worry about not hearing the second crack.
One of the frustrations of these machines, is that they vary so much from one to the other. One roaster's perfect profile is another's charcoal, so sharing profiles isn't always much help. Once I figured-out the idiosyncrasies of my machine, my satisfaction increased tenfold. If you don't mind a fair amount of trial and error in the beginning, roasting with this machine can be a rewarding experience.
As with any product, if you are thinking about buying one, read the forums, not just the reviews.
My i-roast2 is model #40010. There were inserts in the manual for models 40011 & 40012. The later models may include some fixes.