Having only ran custom HUD in one competitive game (not counting crosshairs), I can only talk on what I experienced there... But I'd say custom HUD can definitely be a big advantage and can be qualified as cheating if you're playing by strict tournament rules. I could actually program my HUD to pick out targets for me (and that's really only just the bottom of what could have been done), doing half of my work - only problem was that my CPU and my video card was taking a hit in the process with all the fancy customizations. This in turn gives even more advantages to people with expensive computers.
So while custom HUDs can be amazing and be so much better that default ones... I'm not really sad when I hear that the option will be not available in a competitive game.
P.S. I don't really get the argument that since it's available to everyone, then it's not cheating. Steroids are as available to everyone as are custom HUDs.
P.P.S. Actually, scratch that. Wasn't just one game, just only one game I remembered at the moment of writing. Custom sounds, custom textures, custom HUDs... All make playing/cheating so much easier. At some point, it was such a joke at just how ridiculous it was that I pretty much took up this stance and since stand by it.
