This iron replaces one of the radio shack style. I have had a number of other butane soldering irons before, and hated them. They were very difficult to light, the tended to go out, they leaked butane quickly when off, so you had to fill it before each use. This one, so far, has none of these problems.
And MAN! what a great difference the Weller ML500MP Mini Butane Soldering Iron one makes. It fires up with ease. No more flicking the bic to get the iron going. Heats up fast and is ready to solder in just a min. Gets hot quickly, wide amount of adjustment, reliable ignition, this is the absolute best of the dozen or so pen soldering iron brands Ive tested. Cools down pretty fast too.
The Dremel 4000 is a great little tool that does an awesome job at keeping up with the work load. It is very versatile. No major complaints as of yet. The tool is surprisingly heavy and is pretty big. It makes it hard to do some of the finer projects I was wanting to do because it’s weight and size makes it awkward to handle. I recommend getting the workstation/drill press to hold the tool while you use the flex shaft attachment. You can use the flex shaft without mounting the tool, but it gets in the way and moves around on the bench while working.
The only thing I did notice is when the handle attachment is on the unit then it seems to get rather warm and the hot air tends to leak out and blow on your hand which can get pretty hot. My wife enjoys it almost as much as I do.