[RAZR HD General] iBolski:
First off, you should never be rooted when taking an OTA. That's common knowledge for years. In the end, my issue was a simple IF I would have applied the OTA immediately, rather than holding off and applying it manually via the stock recovery. That had nothing to do with being rooted (which I wasn't since I was back on stock) nor having an unlocked bootloader. Well, that's not entirely true. I had to be rooted to go into the /cache directory and save the soak test file off to my sd card, but after that, I flashed back to stock, unrooted, so technically, being rooted didn't cause my issue. I just had to be rooted in order to access the downloaded file so I could apply it manually myself.

However, having an unlocked bootloader or locked bootloader would not have made a difference. It's only if you choose to do things that an unlocked bootloader allows (easier rooting, flashing a different recovery, installing a custom ROM, etc). If, however, you had an unlocked bootloader but left the stock image as is (no modifications, no root, etc), then it would be exactly the same as if you had a locked bootloader. However, if something were to get borked during the KK install that left you in a position where you couldn't even flash back to JB, then on a locked bootloader, you're hosed until the official FXZ image came out. You would either have to trade your phone in or wait it out. That's with a locked bootloader not rooted.

But, if your bootloader were unlocked, you had a path to revert back to JB at that time and still be running. So, you pick your poison, but to disparage an unlocked bootloader as the cause of all this is incorrect and that's what we're trying to point out. It's more about users who have modified their phones (due to rooting) and they never reverted back to stock.

As for ART or Dalvik, ART is where the bytecode is recompiled into machine-specific binary code, which means faster execution. It does a make a difference. However, not all applications will run under ART at this time. CoPIlot is an application I use and it won't work. However, it seems to be a small number of apps that haven't been updated to run under ART yet.

Dalvik is a machine-independent bytecode that runs on any architecture (in this case, any phone). It's not as efficient as ART since it has to be compiled to a level that any android phone can run it. But, that's where most apps are at this point, but many can and will run under ART. There is are some that won't and they'll have to be updated, but since ART is still a moving target, many developers are holding off on updating their software to be compatible with ART as it could change.

ART is considered experimental. Some say beta at this stage, but even under Dalvik, things are pretty spiffy.

I did have one time where things seem to come to a crawl under Dalvik in KK but a reboot cured it. I was probably running at least 2 days without a reboot, which seems to be the norm anyways. It could also be misbehaving apps. Not all apps are written correctly and they can cause issues and there's nothing the OS can do about it.

I myself am rooted and I run the Xposed framework which won't work under ART. Also, I have the CoPilot GPS app and as I stated, this won't work under ART. It crashes and I have confirmed with the vendor that CoPilot currently does not run under ART.

The beauty of all of this though is that you can switch between the two architectures. So, you can switch to ART and your phone and data stay as is. You can experiment and see if it works. If it does, then you can stay on it. If, however, you eventually find an app that doesn't work, you can then switch back to Dalvik, reboot, and you're back where you left off.