If I could keep one of all the bikes I have tested or ridden for long periods of time, the choice would be the 1952 650B Rene Herse. It did everything well. During the months I rode it, it set two course records, one of which still stands. (I wrote a story about my ride in Bicycle Quarterly Volume 4, No. 1.)
Lightweight, responsive, great handling, with ample gears and good brakes, wide tires that are fast on any road, fenders, some load-carrying capability - and some of the nicest lugwork I have seen anywhere. What more to ask?
The bike is here
http://www.vintagebicyclepress.com/
(The link gives a weight of 23.5 lbs., but that was on less than accurate scale in the days before Bicycle Quarterly. Since then, the weight has since been measured more reliably, and it's closer to 25 lbs. Still lighter than most modern bikes with lights, fenders and racks.)
There are many other wonderful bikes I have had the privilege to ride...
Jan Heine
Editor
Bicycle Quarterly
140 Lakeside Ave #C
Seattle WA 98122
http://www.bikequarterly.com