[HTC One X] lamenramen:
I have tried the following roms: android revolution, chameleon (that pokemon one), slim ics, cyanogenmod9, miui.

None of them improved my battery life appreciably in the sense that at no point did I go, wow, my battery is better. The battery lasts ME 8 hours, maximum. I didn't do any scientific tests with the different ROMs. It seems to me that by FAR the dominant determinant of battery life is the screen. When I see the battery logs/graphs of people on this forum, they report that the X (the international version) can last 24 hours, etc. Really, all that is needed is the screen on time. Why? Because we already know that you can leave this phone on standby for days and days. This is something that nvidia really go right. But wow, that screen, it sucks the juice dry like nobody's business.

When I see logs/graphs that show that the screen is 33% of the battery's usage, I take that to mean that either the phone was not being used much, or was just being used to talk/listen to music, but it definitely could not have been on for very long, or it was on at the lowest possible setting. With my usage patterns, when I'm actually looking at the screen (surfing, writing emails, reading a book) my screen takes up 70% of the battery's juice. On autobrightness, my screen can be on for 3 hrs, 15 minutes. I do not believe I have a faulty battery, nor do I believe that I have a faulty phone. I believe that this is just the way that the One X truly performs. I'm going to pay attention to the iphone 4's screen on time, but before I go and run the test, my impression is that it is around the 5 hour range.

I have no issues with the one x's standby time. It basically doesnt use any power on standby.

The key for me is not that I wish for some magical advances in technology right now. My benchmark is how does this phone perform with regard to the latest and greatest out there? And my impression is that it is a step behind. I'm currently testing my iphone4, and will pay attention to the usage. But all I can tell you is that my usage patterns haven't changed over the last 2 years, while my phone has. My iphone 4 can last me throughout the day, but this one x, most definitely does not. I was completely blown away by the anandtech review that stated that the one x from AT&T, was absolutely the most battery efficient phone currently in production. I have the one x int'l version, and it is still no slouch and compares favorably to the 2 yr old iphone 4 acc to anandtech's batt benhmarks. So when I got my one x int'l version, I was astonishingly disappointed.

That said, I would not take anandtech's benchmarks literally. They're good for relative comparisons. They're also famous for showing how battery efficient the macs are, and in no way do I ever approach the battery runtimes they report.

To me the only remaining question is if getting the S4 processor inside my phone would improve battery life to iphone 4 levels. I believe that it may, even though I just said that screen time is the dominant factor. I do recall noticing that when I'm just reading an ebook, and the processor is idling, the battery drain isn't actually nearly as fast. So maybe the cpu will improve. My biggest dilemma is whether having updated, rewritten drivers for the tegra 3 really can do wonders. I am skeptical that a) this will ever be done in a timely fashion b) if drivers will have a big enough effect on a fundamentally older architecture and manufacturing process. As we know the tegra 3 uses a 40 nm process, while the S4 uses a 28 nm process.

Truth be told, in all honesty--my biggest mistake was ever buying the iphone 4. For all that that phone can not do, and my philosophical differences with their approach to products, I did not realize until now that the things that that phone does, it does incomparably well...and that phone has checked off all the right boxes for me: battery life, perceived speed, gorgeous screen, design, etc.

Are there two kernels? The ICS kernel and the tegra 3 kernel? When I put cyanogenmod9, I have the ICS kernel, right? We have no control over the tegra 3 kernel? Just not sure if ICS source code can affect the tegra3 kernel.