I'm using a Galaxy S3 using the AT&T stock 4.4.2 configuration. The performance overall seems sluggish. I've already gone through the usual checklist of deleting/disabling unused apps and files (except for the built-in ones as I don't have root). Would installing a custom ROM and/or rooting give a large performance increase? I'd rather not go through the hassle if the only major improvements are to the UI.