A study published in Clinical Biomechanics (online Sept 2012) looked at pain levels in people aged 40-65 with plantar fasciitis. Using a visual analogue pain scale, they compared the use of foot orthotics to toning shoes to foot orthotics and toning shoes.

The pain scores on the VAS for the 3 conditions were:

Rocker shoes and foot orthotics:  9.7mm
Rocker shoes: 30.9
Foot Orthoses 29.5

So the rockers shoes combined with foot orthoses produced the best results and the authors concluded:

The findings indicate that a combined prescription of rocker sole shoes and custom-made foot orthoses had greater immediate therapeutic effects compared to when each treatment had been individually prescribed.

– this is not a very commonly used intervention for treating plantar fasciitis
– this was an acute intervention and the participants were not followed over time
– the VAS is not the most validated measure for pain levels in plantar fascitis

For more on plantar fasciitis, see this post.and this essay. Run Junkie has one of the sensible approaches to it.