I'm on my 2nd X, 3rd battery.
First phone, first battery ordered the night they became available. Phone arrived, battery life was terrible (4-5 hours max, nothing odd running on it). Called Verizon, they sent a 2nd battery. This one worked better and would require charging every 24 hours. I assume this is normal and am happy. Then my ringer/speaker stopped working, back the phone (my wifes Droid) to Verizon.
We try various incantations/resets/voodoo stuff and they tell me they're sending me a new phone - in two days!
Almost a month goes by and my new phone arrives - it's really new and has a battery/charger/etc with it. I'm apprehensive about using a new battery, given my experiences with the first battery but I charge it and activate the phone. I download the apps I had on the original phone immediately, and set up the phone EXACXTLY the same as the original (I'd written down all the settings so I could get it right). This phone and new battery has been running 24 hours and the battery is still at 70% - I've done my usual daily stuff with it, taken/made calls, did email, some browsing, etc.
It's clear to me not all X's are created equal.