My two cents: if I was looking to get a new Verizon phone, and the Incredible and X were both out, I don't know which I'd choose. I'd probably go play with them in a store and decide.
That said, I have an Incredible, and I'm not looking to upgrade every 3 months when a new phone with slightly better specs comes out. The advantages I see of the X aren't killer ones (to me), so I'm not going to shell out another couple hundred bucks to stay on the bleeding edge, just to have to repeat the cycle again in a few months.
As awesome as it would be to always have the newest phone, it's not worth the financial punch I would take ($800+ a year, assuming you stay faithful to a single carrier), nor is it worth the frustration of just finally getting comfortable with your phone before you have to replace it.
I have a hard time understanding anyone who upgrades from the Incredible to the X, not because the specs aren't [slightly] better, but because they couldn't have had the Incredible for more than a few months yet.