AG, I'm assuming you're following the P&D plan as you've posted on that thread. I've used the 5mile recovery runs to break in new shoes, and a couple of other posts have mentioned doing the same.
It does depend on the shoes to some extent - I've got a new pair of my current shoes (Saucony Mirage) that had one 5m recovery and then were used for my 8m Aerobic run today, and they're likley to be used in a 10+ mile run on Sunday.. I also got a pair of lightweight Saucony Fastwitch for Xmas and I've run a few 5m recoveries in them and will gradually start using them for longer runs (with the aim of using them for forthcomng half- and full- marathons).
So it depends a bit on how closely your Ghost's fell like your old Omni's