So here I was, sitting and watching the world get .340 on the DX through the OTA. I was using Apex 126.96.36.199 so I couldn't go through the OTA. Everyone talked about just sbf back to stock and then getting the update, but I was too lazy to do that. Here's another way.
A while back I posted 928's link to their deodexed roms. They also include a stock odexed rom in there
So I downloaded the 928Droid-BackToStock-DroidX22-OTA-Odexed.zip and installed it as another rom.
Then I installed z4root (since I lost root after the .340 update) and got root back.
Once that was done, I installed a different ROM
I didn't delete data or cache at any point and it worked fine.
So there ya go, the easy way to go back to .315 stock and then update to .340.
btw, you have most likely kicked yourself in the behind for not creating a nandroid backup of the stock .315 so you could just go back to that to upgrade to .340. Don't make that mistake again