Join Date: May 2011
Location: Upstate NY
Bikes: Bianchi San Mateo and a few others
I have a 1991 Cannondale SM400, whose frame is similar to that one. If it fits you, and is in good mechanical shape (which can only be checked in person), it would make a solid commuter. As a commuter, it's also nice that the frame and fork have eyelets for fenders and/or racks. Rigid frame and fork are good for commuters, too. I'd definitely grab it, no second thoughts, for the listed price of $99.
One possible catch: In the ad, the bike is listed as 18", which would fit someone around 5'9", give or take a few inches. To my eye, that bike looks an awful lot like the 16" SM400 I have, although the 16" bike in the 1987 catalog looks even smaller. Personally, I'd just check out the size in person. When looking at Craigslist ads in general, it's healthy to doubt the listed size (if there is one). They're often wrong. Just confirm it in person.