I'll toss in my two cents late in the game.
I wouldn't count on getting much out of the doctrine of equivalents (DoE). Since prosecution history estoppel is a limit on the DoE, it amounts to a limitation on the scintilla of extra coverage you might get from the DoE. It's far, far, far better to get the claims right.
For me, the only time Festo crosses my mind is when I think the law supports the claim as it is (actually, as filed) but I can see a minor modification would appease the examiner. If the claim (or at least the element of the claim at issue) isn't clean (i.e., has been amended), Festo already applies and there's not much to save. However, if the claim is clean (i.e., as filed), I'll press harder when the examiner is wrong but could be appeased by an amendment.
Any other situation, forget Festo.
Regards.
We agree on another principle! There have been only a handful of affirmances of infringement under DOE by the CAFC in recent years. You just aren't going to win often on DOE.