Pros: Let the extreme speed of a Dremel tool's motor work for you.
Cons: This is a finesse tool (not one based on torque). Don't try to muscle it.
I've had my Dremel 395 for almost 7 years, and for appropriate jobs, it is really fun to use.
You can buy the motorized hand units separately (and the same goes for all the bits & attachments), but you'll spend considerably less if you buy them as a package like this one, which includes a case for the tool and a range of accessories. This kit is comprised of the tool itself, a special wrench for the tiny chuck, a cable-like extension for special work, some cutting bits, some grinding stones and wheels, mandrels and collets to hold the bits and align them precisely, some polishing pads and a little stack of abrasive cutting wheels in its own container. The instruction manual is thick but readable (as well as an essential reference) and the case has a special slot to store the manual. The Dremel people think of everything.
The thing cuts steel pipe as quickly (and more neatly) than a hacksaw; it's a blast to use as a router in cabinet-quality work; if the appearance of a finished project really counts or the beauty is in the details, odds are a Dremel tool is what you are after.
You will do well to read the directions, heeding the advice to get the feel of the tool when the motor is spun up, and to let its high-velocity motor do the work. At 30,000 rpm, you can feel the gyroscopic effect very slightly, but it's easy to get accustomed to, and you'll be using this tool at its best handling it almost like an oversized pencil.
With most power tools (and American tools in particular), the idea is go ahead and press on the damned thing as hard as you like and take advantage of its low-speed, high-torque motor. With a Dremel, it's just the opposite: That ultra-fast spinning gets it done. If you bear down on a Dremel, you may ruin it or break something.
Example: The abrasive cutting wheels are extremely brittle. You had better hold them steady in the groove while you're cutting pipe or whatever. Cock the wheel sideways even a bit and it will shatter. Wear your goggles, too, because even if you are careful with the abrasive wheels, they are prone to break, and with the things whirling at up to 30,000 rpm, pieces of the discs can fly out of there enough to damage your eyes severely.
Thankfully, the cutting wheels are quite cheap. Depending on how much heavy-gauge metal you cut, you may count on expending a few of those.
Not so with a wide variety of Dremel bits, which are extremely well-machined of special tungsten alloys with diamond tips & so forth. Compared to most bits people are accustomed to using, the Dremel pieces look like toys. That's a function of their diminutive size--but don't let the scale fool you. Dremel bits are manufactured to the quality of self-winding Swiss watches. They have a jewel-like finish and a price to match. But if you are careful with them, they will last a long time.
Yes, the bits and some of the accessories are pricey, but very, very well-made. And you know what else? So far all the Dremel stuff I have found has been made in the USA.
If you tend to be hard on tools or you just cannot resist giving it the whammy, a Dremel tool may not be for you. I mean, there are guys who can produce fine sculpture with chain saws. A good way to think of a Dremel's strength is not to apply any more force than a watchmaker would. Some folks just cannot get the hang of that philosophy.
If you need to sling a Dremel tool around in the mud or someplace like that, I'm not sure how well it might hold up. But otherwise, simple precautions like storing it in its case should suffice to protect your investment.