English Ivy on trees, Good or Bad!

Where I use to live I had large trees and a number of them had english Ivy growing all over them, it didn't seem to effect the trees
(Maple and Wild Cherry) any but it had just started growing on them about 14 years ago. By the time I moved the Ivy was half way up the tree (approx 40 feet up) and completely around the tree about a third of the way up, about 25-30 feet. However, I've heard from different people it is not good for the trees to let the Ivy grow up on them that far for this or that reason. I've also heard it doesn't effect them one way or the other. Where I live now I have a lot of very large trees and I have english ivy that I currently keep under control, none on the trees at this time. I like the look, but it's easier to ask now than to try and get it off later. I don't want it on every tree just a few in the shady part of the yard.

Does it hurt the trees to have English Ivy growing on them in mass? Mostly Oak and most of them 75'-100' tall. I don't think it does, but then again it might over a long period of time, I done moving and I like these trees and I bet they'll be here when I'm gone. So I don't want to damage them if I can avoid it.

Thanks
Dave

We moved in to a new-to-us house about four months ago and the landscape had been terribly neglected - EVERYTHING is covered in english ivy. I talked to an arborist who assured me the only problem with it growing up trees is that it will pull the bark off if you try to remove it, opening the tree up to disease. I just keep the vines cut when they grow down to where I can reach them and otherwise don't worry about it.

Thanks KayJones that is what I thought as when English Ivy gets ahold of something it doesn't let go. I seen it pull stucco off a house when you tried to remove it. I know it's parasitic to some degree but I don't think enough to cause damage.