What are your impressions of the Braille Pen Slim?

Hello all,
I just came across the Braille Pen Slim by Perkins while looking for bluetooth accessories for the iPad. I have a Focus14, and I use that a fair amount, but what I'm REALLY looking for is an even more portable way to input Braille, no display required. Ideally, this would also be something I could use in class to interface with my Mac. What are your impressions of the Braille Pen Slim, if you have one? Is it appreciably smaller than the Focus14? I'd like it to be able to slip unobtrusively into the front compartment of my backpack or a jacket pocket. How is the battery life? Is typing on it fairly easy/what are the keys most like? I've tried the Refreshabraille 18, and can't stand the keys on there because they're so small and close together.
Any impressions you guys can give me would be great!
Thanks,
Megan