I'm afraid I don't know anything about the Jamis. My Trek was almost $400 but there are others in the same line that are closer to $300. You might check out the Trek site (
http://www2.trekbikes.com/en/) and then search some of the hybrid models here for comments, if you're interested. But the Jamis may very well be an excellent choice! Here's the site for my bike, if you'd like to compare:
http://www.trekbikes.com/bikes/2004/citybike/7200.jsp#
The latest I've ridden is about 9:15 p.m., just past dusk, so most of my riding has been in the daytime and I have felt the flag was very effective. I attached mine to the back of my rack but since you're not getting a rack at first, you may need to attach it to your seat. I also carry my bike on a car rack and the flag has weathered 65 MPH trips on the back of my car just fine. I think it even helps as a safety feature back there!
