We can thank Jose Luis Castañeda in Guadalajara, Mexico for giving us a link to photos of his rooftop garden. He has done a great job using Larry Hall's rain gutter sub-irrigation system. His pristine white bucket planters in perfect alignment on the rain gutter reservoirs have a pleasing look even without decorative concealment.
If these were on my patio, it wouldn't bother me at all to look at them. I also wouldn't be bothered by having to water them individually since the rain gutter float valve makes watering automatic.
Note in the bottom photo that he is also experimenting with sack planters on the rain gutter system. He also shows a bucket planter with side planting holes a la sack gardens. I'm not sure if it is irrigated on the rain gutter system.
I related to Jose's comment about the difficulty in changing embedded human habits. This is particularly true in home gardening when so many of its practices are based on folklore and family tradition often passed down from mother to daughter.
Since January 2010 i've been teaching people in Guadalajara, Mexico about sub-irrigation and believe me, hasn't been easy. At first, people don't understand the system, later they do, but they keep skeptical, finally they don't put into practice what they have learned, maybe i'm not that good at teaching. What i mean is that is hard to remove the idea of top watering and drain holes, i'm guessing this paradigm is worldwide.
Take a look to this photo album https://picasaweb.google.com/116282453914033980750/AltairaSubIrrigatedRooftopVegetableGarden it's our sub-irrigated garden on a rooftop.