I think there is a distinction between a support role and a "line" role that still exists. The 'purpose' of support roles is to be of service, hence in certain organizations where I have worked a business would stake claim to their 'own' HR person, Finance person, IT support person etc.

How one views oneself goes a long way in how one reacts to this. Some support people are too aligned to their professional and functional identities for them to see themselves as "business people" (I myself am guilty of this fact !) Others become identified first as business people and then as functional people.

This according to some, like Wayne Brockbank is the way to go forward (Can't find the link, but in one interview he said he was exasperated with one of his HR students who didn't want to experience other parts of the business!). You can see evidence of IT services firms trying to build domain competence as a win for this strategy.

So, is there a best way to go about it? Well, if your goal is to "be at the table" , it is important to drop functional blinkers and see things as a general management perspective. There will be discomfort at letting go of your trusted and used skills, and terror at stepping out into the unknown details of other functions. But who said learning was easy?