I find that vehicles give me more room than when I'm perched on a conventional machine, a small dayglo flag on a tall 4mm diameter glassfibre pole fixed to the seat helps in busy traffic.
Speed wise on the flat even I can hit 25mph and average 15mph over long distances and the view of the countryside isn't that much different to that from an upright. Climbing is however a bit worse as you can't stand on the pedals but if you go down the hills really quick you get up the other side a lot easier and overall progress is close to uprights.
Comfort is streets ahead of any upright, no more back pains, or shoulder pains or neck pain, or numb hands or numb nuts. Pedalling lying down uses slightly different muscle groups to an upright though so getting the best out of them takes time but this also means moving back to an upright isn't easy especially as they seem
very high up but many riders wouldn't want to return to an upright as recumbents are addictive.
Visibility to the rear is worse as you can't easily glance behind even when stood still, so mirrors are useful if not essential, but most of the time you can be moving at about the speed of the surrounding traffic so it's not as bad as it sounds. Brakes and cornering are out of this world. (see the video below!)
The Lands End John O'Groats solo cycling record is held by a Windcheetah, a fully faired version at a smidgen over 41 hours, an average of about 20mph...and a peak of 70+ mph
The UCI banned recumbents in the 1930's which is as big an endorsement as you're ever going to get. Mike Burrows is a genius of an engineer, he's going faster now than he did 40 years ago, he admits the 'engine' is worse, the machines he produces are better.
This is a link to the video that has a long standing broken link at the Windcheetah site showing the ultimate cornering if you are very brave.
[ame]http://www.youtube.com/watch?v=8cxBkHGaOPg[/ame]
and this is Adam Hart-Davis, another Windcheetah owner showing his 'modified' version
[ame]http://www.youtube.com/watch?v=PAeyoSI81bo[/ame]