I don't really bother about them, Susan, except when I'm thinking of (non-poisonous) spring bulbs.
So I tend to complain about them around this time of year.
I don't believe we have any problem with them attacking the root systems of perennials, girdling trees, damaging the lawns and the like.
My friend David Tomlinson, at Merlin's Hollow, Aurora, uses two inches of wet maple leaves on his extensive perennial beds each fall.
This makes a great habitat for voles, so he uses warfarin in beer cans, to save his sheets of crocuses.
He enlarges the hole in the can, large enough only for a vole to get in.
He never eliminates all the voles, but feels this keeps the problem in check.
Relevant things: I dig in organic matter, don't use mulch and though I maintain perennials close together, don't use plants as "ground cover".
I'd also be willing to believe that burrowing animals like voles do have some beneficial effect on our (upgraded) clay flower beds.
I don't see any evidence of natural vole predators in the garden and have been very hostile about a former neighbour's cat which regularly used my pile of potting soil as a cat box.
My solution with spring bulbs is to just plant more each fall.
