Our district's gifted testing starts with a screener (KBIT and TOMAGS) and then moves on to WISC-IV. I'm glad to have the IQ info, but have no intention of telling my kids their "numbers". Interestingly, DH and I didn't learn our actual IQs until we had our oldest tested -- apparently at that point each of our parents decided we were old enough, or mature enough, to know. We were both in gifted programs at school as kids, so there was a general knowledge that we were at a certain level which I think parents thought was enough info.
I'm glad we have the info, as it helps us advocate for our kids better. Since the testing was done through the school, the administration "trusts" the data, so to speak. I don't think we'd be pushing as hard for math acceleration for our youngest without the info from the TOMAGS and WISC. Our district does a decent job with differentiation for MG and HG kids, so I feel like our two older kids are being well served, but our youngest is just at a different level with respect to math and I don't think I would have appreciated that without the testing, because he doesn't present himself that way.