My main requirement from cycling is to be able to commute 32 miles to work across semi-rural West Sussex, England, Europe, without using my car or the train, while getting a healthy amount of exercise, fresh air and countryside good feelings, while not being stressed by traffic jams and train cancellations (in fairness, the trains have been better this year after teething problems with new rolling stock).
The closest I have approached this so far is with an upright bike (Trek 1400), 1 hour 45 minutes inward journey (18 mph average, including junctions and traffic lights), then take the train all the way back. At 39 years old, I feel this is not going to get any better.
A high-end bike shop in Portsmouth, after suggesting minor efficiency improvements like tri-bars and carbon wheels, realised that I was happy to employ drastic measures, and suggested a recumbent as a way of shaving off 10 minutes in the hour. And a New Scientist magazine (late 2004) reported around 80mph records for a fully faired recumbent (although they take an hour to set up so not much good for commuting). One of the few fully-faired recumbents on the market is the Lightning F-40. Only one supplier in Europe had one in stock for me to test ride, in southern Germany. Since they cost about 5000 United States dollars, there was no way I was going to mail order one on spec, so I travelled to Germany to check it out.
After falling off a few times, I was happily doing 32 mph on the flat, nil wind. So I ordered one. It's a lot of money, but peanuts compared with moving house or more car depreciation.
As I see it, the issues regarding recumbent v. upright, for this commute ride, are:
1. Aerodynamic efficiency - frontal area: Being recumbent instead of upright clearly reduces frontal area, with some aerodynamic improvement. But without fairing, it is still very turbulent, so only a few mph improvement, once one has developed the different muscles. Nevertheless, recumbents were banned circa 1910-1930 in international cycle races because of their inherent aerodynamic advantage.
2. Aerodynamic efficiency - fairing: Fairings improve efficiency on upright and recumbent bikes, but again they were banned early this century in international cycle races because of their inherent aerodynamic advantage. Note that a rear-only fairing (looks like trailing edge of a wing) on its own provides more advantage than a front-only fairing on its own, and is more handy for luggage. For my purpose, a full fairing was applicable, though more expensive.
3. Weather : For protection against rain and cold, a full fairing does most of the job. This was an unexpected benefit - on an unfaired upright, I have to spend about 15 minutes in the morning looking for and putting on overshoes, Sealskin gloves, etc., and then more time hanging it all up in the office to dry. And just the psychological boost of not having the wind and rain blasting into my face makes it feel easier.
4. Pedalling efficiency: Recumbents lose on steep hills. Very laid back recumbents are worst, since you just slide up the seat. The Lightning F-40 is quite upright, and breaks even up to about 10% grade.
5. Comfort: I wore upright cycling shorts (I think this means something different in the U.S.; I am referring to the black Lycra/Spandex short trouser item that is worn on the outside) and regretted it very quickly. Loose-fitting shorts are better, and this is also a benefit when off the bike, e.g. in train or car, because I don't find cycling shorts comfortable then either.
Saddle - much more comfortable, more of an armchair, you can stop and just sit there and relax. I have to get off an upright to do this.
Handlebars - needed only for control input, so much lighter on fingers and wrists.
If anyone knows of a faster way to do this commute trip by bike, please let me know.
I got a new action bent and its taken me quita bit of work to make it rideable......I am writing an article about it for Recumbent Cyclist news magazine.....so I will post more info later.... 
