I too have that fever!! And by chance i am looking at those exact bikes. Right now the Cannondale Capo has caught my eye. I'll be driving to an LBS to check out the langster today and see what I think.
I really like the look of aluminum frames (ie capo, IRO jamie roy, pista concept not sure about langster?) I have ruled IRO out because i have to admit I am an appearance ***** and the Jamie Roy is the only one I really liked, and they are out of that frame till mid july. Basically, I could come home today with a langster, or wait a week for a cannondale.
From what I have read the Capo has a top notch frame with mediocre components, similar to the langster. The capo is a little more than the langster ($800 vs $750)
good luck!