I do like the look of the hanging Barn Lights, but they are not very efficient reflectors. You could surface mount all the conduit and hang just about anything.
What are you after the look or an easy way to hang the lights? If I were you I would mount boxes in the ceiling and use romex. That would be cheaper.
Here is a link to a barn light...
http://www.vintagehardware.com/proddetail.php?prod=28491
Volt x amps = watts
also
watts/120volts = amps
The fixtures will have a max rating on them, you should use that to figure the worst case. Electrical Code is all about protecting you and the next guy who owns the property. If the circuit is going to have 10 of these say 60 watt maximum fixtures, you add them up and come up with that maximum value in watts and divide by the voltage. So 600 watts divided by the voltage (120vac) is 5 amps. A single lighting circuit can handle 15 amps. Look and find what else is on the circuit. If there are electrical outlets on there as well, then you may have a breaker trip nuisance. It would be safe, just a nuisance. If you plan on using the CFL’s then they should only require 2 amps in the above rather than 5 amps and you could combine the lighting and the outlets. Problem in doing this is that if you were ever to have an outlet load and it take out the breaker, you are in the dark.