I've been having the same VERY bad battery life (have to start charging at about 2pm after taking the phone off the charger at around 5am). My X used to last for 24 hours at a minimum, sometimes up to 48 depending on usage.
I'm curious what's different on my phone - mine is also showing the cell standby is higher than anything else. So, for the 4th time now I've SBFd and I'm re-installing, but this time I've cancelled the 5 apps that my system would automatically download from the market. We'll see if that has something to do with it.
I'll report back in the next few days.