My trusty ancient Dremel tool died. It was the old type that had the plastic shaft as a failsafe that constantly broke and I constantly fixed. Now I am in the market for a new one but am confused by the reviews. Are they junk now since Bosch took over? I see horror stories of smoking burning sparking tools. I read the variable speed models have a circuit board in place of the old analog speed switch, and it gets dust clogged overheats and fries. Now they have a 4000 series that supposedly addresses all these issues but I'm leaning towards the simple models, like the 100 and 200 that are just on/off. What are you guys using?