I'd second the recommendation for variable speed. I have two Dremel-type tools, one from Sears (which is a Dremel, just rebranded Craftsman), and one from Grizzly Industrial. Both are corded, variable-speed tools, with a decent range - I think 8K to 30K RPM.
The Craftsman's been with me for probably 20 years (yeah, I was that kind of kid), and is still going strong. I think I've cleaned the motor brushes once or twice, but have yet to replace them. One drawback is that the switch is both power and speed - you have to reset the RPM each time you power on. Of course, a powerstrip could fix this.
The Grizzly is made in China, undoubtedly, but is working just fine. I mainly got it for the flex-shaft and stand, which are worth the admission price by themselves. For any kind of long-term use, the flex-shaft is much lighter and more comfortable. Also, it's got a separate power switch, so RPM can be left adjusted between sessions.
http://www.grizzly.com/products/h6155
I'm kind of cool on the cordless concept, but most of the work I do, I can bring the piece to the tool. If you've got projects where power is inaccessible, they might be worth the price. For the majority of my needs, though, I'll take the lighter overall weight over not having cords to plug in. Just my opinion, though.