Have a LWB Burley that started out life as a Koosay. Replaced the seat with a RANS seat, then most of the other components with high end stuff as they wore out after 4 or 5 thousand miles. I replaced the cranks with 153mm cranks from 'Bikesmith Designs' and geared the front triple rings down a bit to make up for it, because of a previous stroke and weak left leg, which now is completely gone, thanks to that bike!
I'd probably have an upright bike or two in my stable, particularly for off road MTB'ing, but get severe pain, weakness and numbness in the left leg if I ride an upright much.
The bent handles everything from paved roads to loose gravel rails to trails paths just fine, so guess I'll have to live without any serious single tracking. Climbs well with the shorter cranks and lower gearing, and I find I spin up hills at about the same speeds as the upright guys in a similar age and fitness group.
Looking at a Rans V3 aluminum for more serious roading. Maybe next year.......