I have a rotary tool from black and decker, I used to have a battery dremel but the bat died out and replacement was more then 1/2 the cost of a new tool.
The BandD is amazing.
http://www.walmart.com/ip/Black-Decker-3-Speed-RTX-Rotary-Tool-Model-RTX-B/9714694
I mean it's only $30 but don't let a slim price fool ya, this sucker is amazing for this work.
The biggest thing to remember is no matter what one you get - it's how you use it. Forcing cutting blades or PUSHING the tool into the item will turn out badly - let the tool do the work, the cutting wheels just barely touch the material to cut - they sand away at it until a cut is made, if you push a cutting wheel into fiberglass - it's more then likely going to shatter and possibly do damage to your item or worse, yourself. At the first sign of chipping/wear - discontenue use of the cutting wheel and replace it. An uneven cutting wheel (a dent in one side, etc) will only cause problems and is only a matter of time before it shatters. Gentle touches win with Rotary Tools, especially Powered Ones.
It's got multi speed support for all needs (cutting, sanding, grinding, etc) plus the grip is amazing and you can even get special attachements and blah blah.
The only thing I don't like is sometimes when using it - your hand blocks the vent - it'll get warm pretty quick but if you keep your eye on the vents it works out well.
OH and remember to get the right size collet nuts for your parts - if your going for anything but standard use. I had to figure this out the hard way. lol.
Typically you need many (50+) Cutting Wheels and Sanding Drums, these are the most commonly used things, and they are inexpesive (especially if you find them in bulk of like 50 or 100 packs online) then when you go through one you don't feel so bad. Reinforced cutting wheels are wonderful for 'near finished' cutting, through multiple layers of bondo/fiberglass etc but you can get similar results just using more cutting wheels, depends on price when I buy them.
Drill attachments are good too, in case you want to do wiring/add parts/etc
but most the other stuff is a rare use - I haven't etched anything into anything yet or polished anything.