Actually, I don’t agonise over split infinitives. But people sometimes do. And I don’t think anyone should (any more than they should worry about sentences starting with ‘and’ or ‘but’). I recently self-edited an email from:
‘Are you asking us both to write and design this 1-page leaflet?’
to read:
‘Are you asking us to both write and design this 1-page leaflet?’
In fact, it could have been brought into line simply by removing the word ‘both’. But the point is – particularly when copywriting for business – if a grammatical rule gets in the way of clarity, then it’s not a rule worth observing.