In reply to ebdon:
The burns and rivers fall rapidly once it stops raining, so (on current forecasts) you should be OK to start with, but some more rain is forecast for late Saturday onwards. The part I would be most worried about is upper Glen Feshie, where you might have to cross a rather large river because there will almost certainly have been fresh landslides in the stretch where the path is most tenuous (around NN862900 -- look at it on OS Get-a-Map). The estate track crosses the river three times, at places which are OK in a dry spell but iffy to impossible in higher flows. Ideally you stay on the true right bank all the way to Achlean.
hth